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‎HappyNumber/happy_number.dart

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/*
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-* Happy Number *-
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Write an algorithm to determine if a number n is happy.
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A happy number is a number defined by the following process:
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Starting with any positive integer, replace the number by the sum of the squares of its digits.
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Repeat the process until the number equals 1 (where it will stay), or it loops endlessly in a cycle which does not include 1.
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Those numbers for which this process ends in 1 are happy.
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Return true if n is a happy number, and false if not.
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Example 1:
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Input: n = 19
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Output: true
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Explanation:
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12 + 92 = 82
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82 + 22 = 68
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62 + 82 = 100
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12 + 02 + 02 = 1
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Example 2:
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Input: n = 2
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Output: false
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Constraints:
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1 <= n <= 231 - 1
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*/
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import 'dart:collection';
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import 'dart:math';
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class A {
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/*
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Complexity Analysis:
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Time Complexity: O(n*log(n)).
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Auxiliary Space: O(1).
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*/
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// Runtime: 559 ms, faster than 36.59% of Dart online submissions for Happy Number.
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// Memory Usage: 140.6 MB, less than 95.12% of Dart online submissions for Happy Number.
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bool isHappy(int n) {
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int slow, fast;
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// initialize slow and fast by n
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slow = fast = n;
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do {
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// move slow number
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// by one iteration
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slow = numSquareSum(slow);
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// move fast number
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// by two iteration
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fast = numSquareSum(numSquareSum(fast));
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} while (slow != fast);
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return (slow == 1);
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}
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// Utility method to return sum of square of
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// digit of n
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int numSquareSum(int n) {
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int sumSquare = 0;
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while (n != 0) {
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sumSquare += (n % 10) * (n % 10);
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n ~/= 10;
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}
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return sumSquare;
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}
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}
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class B {
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/*
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Time Complexity: O(n*log(n)).
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Auxiliary Space: O(n) since using extra set for storage
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*/
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// Runtime: 536 ms, faster than 53.66% of Dart online submissions for Happy Number.
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// Memory Usage: 143.7 MB, less than 29.27% of Dart online submissions for Happy Number.
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bool isHappy(int n) {
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HashSet hs = HashSet();
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while (true) {
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n = numSquareSum(n);
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if (n == 1) return true;
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if (hs.contains(n)) return false;
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hs.add(n);
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}
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}
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int numSquareSum(int n) {
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int sumSquare = 0;
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while (n != 0) {
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sumSquare += (n % 10) * (n % 10);
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n ~/= 10;
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}
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return sumSquare;
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}
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}
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class C {
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// Runtime: 484 ms, faster than 78.05% of Dart online submissions for Happy Number.
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// Memory Usage: 140.6 MB, less than 95.12% of Dart online submissions for Happy Number.
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bool isHappy(int n) {
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if (n == 1 || n == 7) return true;
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int sum = n, x = n;
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// this loop executes till the sum of square of
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// digits obtained is not a single digit number
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while (sum > 9) {
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sum = 0;
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// this loop finds the sum of square of digits
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while (x > 0) {
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int d = x % 10;
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sum += d * d;
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x ~/= 10;
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}
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if (sum == 1) return true;
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x = sum;
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}
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if (sum == 7) return true;
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return false;
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}
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}
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class D {
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// Runtime: 261 ms, faster than 100.00% of Dart online submissions for Happy Number.
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// Memory Usage: 139.3 MB, less than 100.00% of Dart online submissions for Happy Number.
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/// > It takes a number, adds the squares of its digits, and returns the result
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///
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/// Args:
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/// n (int): The number to be checked.
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///
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/// Returns:
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/// The sum of the squares of the digits of the number.
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int solve(int n) {
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int sum = 0;
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for (int i = 0; n != 0; i++) {
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int r = n % 10;
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sum = sum + r * r;
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n = n ~/ 10;
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}
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return sum;
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}
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bool isHappy(int n) {
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int i = 10;
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/// A loop that checks if the number is happy.
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while (i > 0) {
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int happy = solve(n);
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if (happy == 1) {
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return true;
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}
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n = happy;
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i--;
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}
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return false;
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}
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}
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class E {
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// Runtime: 309 ms, faster than 100.00% of Dart online submissions for Happy Number.
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// Memory Usage: 158 MB, less than 7.32% of Dart online submissions for Happy Number.
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int sums(int n) {
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int ans = 0;
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while (n != 0) {
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//ans += pow(n % 10, 2);
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ans += pow(n % 10, 2).floor();
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n = n ~/ 10;
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}
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return ans;
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}
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bool isHappy(int n) {
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int s = sums(n);
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int f = sums(sums(n));
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if (f == 1) return true; //for case n==1
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while (s != f) {
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if (f == 1) return true;
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s = sums(s);
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f = sums(sums(f));
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}
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return false;
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}
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}

‎HappyNumber/happy_number.go

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package main
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/*
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Runtime: 0 ms, faster than 100.00% of Go online submissions for Happy Number.
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Memory Usage: 2 MB, less than 93.92% of Go online submissions for Happy Number.
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*/
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func isHappy(n int) bool {
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i := 10
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for i > 0 {
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happy := sums(n)
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if happy == 1 {
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return true
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}
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n = happy
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i--
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}
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return false
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}
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func sums(n int) int {
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var sum int = 0
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for i := 0; n != 0; i++ {
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r := n % 10
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sum = sum + r*r
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n = n / 10
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}
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return sum
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}

‎HappyNumber/happy_number.md

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# 🔥 Happy Number 🔥 || 5 Solutions || Simple Fast and Easy || with Explanation
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## Solution - 1
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### Complexity Analysis
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- Time Complexity: O(n*log(n)).
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- Auxiliary Space: O(1).
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```dart
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class Solution {
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// Runtime: 559 ms, faster than 36.59% of Dart online submissions for Happy Number.
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// Memory Usage: 140.6 MB, less than 95.12% of Dart online submissions for Happy Number.
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bool isHappy(int n) {
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int slow, fast;
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// initialize slow and fast by n
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slow = fast = n;
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do {
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// move slow number
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// by one iteration
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slow = numSquareSum(slow);
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// move fast number
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// by two iteration
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fast = numSquareSum(numSquareSum(fast));
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} while (slow != fast);
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return (slow == 1);
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}
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// Utility method to return sum of square of
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// digit of n
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int numSquareSum(int n) {
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int sumSquare = 0;
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while (n != 0) {
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sumSquare += (n % 10) * (n % 10);
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n ~/= 10;
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}
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return sumSquare;
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}
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```
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## Solution - 2
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### Complexity-Analysis
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- Time Complexity: O(n*log(n)).
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- Auxiliary Space: O(n) since using extra set for storage
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```dart
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class Solution {
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// Runtime: 536 ms, faster than 53.66% of Dart online submissions for Happy Number.
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// Memory Usage: 143.7 MB, less than 29.27% of Dart online submissions for Happy Number.
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bool isHappy(int n) {
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HashSet hs = HashSet();
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while (true) {
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n = numSquareSum(n);
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if (n == 1) return true;
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if (hs.contains(n)) return false;
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hs.add(n);
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}
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}
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int numSquareSum(int n) {
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int sumSquare = 0;
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while (n != 0) {
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sumSquare += (n % 10) * (n % 10);
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n ~/= 10;
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}
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return sumSquare;
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}
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}
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```
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## Solution - 3
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```dart
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class Solution {
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// Runtime: 484 ms, faster than 78.05% of Dart online submissions for Happy Number.
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// Memory Usage: 140.6 MB, less than 95.12% of Dart online submissions for Happy Number.
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bool isHappy(int n) {
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if (n == 1 || n == 7) return true;
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int sum = n, x = n;
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// this loop executes till the sum of square of
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// digits obtained is not a single digit number
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while (sum > 9) {
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sum = 0;
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// this loop finds the sum of square of digits
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while (x > 0) {
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int d = x % 10;
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sum += d * d;
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x ~/= 10;
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}
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if (sum == 1) return true;
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x = sum;
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}
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if (sum == 7) return true;
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return false;
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}
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}
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```
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## Solution - 4
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```dart
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class Solution {
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// Runtime: 261 ms, faster than 100.00% of Dart online submissions for Happy Number.
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// Memory Usage: 139.3 MB, less than 100.00% of Dart online submissions for Happy Number.
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/// > It takes a number, adds the squares of its digits, and returns the result
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///
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/// Args:
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/// n (int): The number to be checked.
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///
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/// Returns:
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/// The sum of the squares of the digits of the number.
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int solve(int n) {
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int sum = 0;
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for (int i = 0; n != 0; i++) {
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int r = n % 10;
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sum = sum + r * r;
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n = n ~/ 10;
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}
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return sum;
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}
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bool isHappy(int n) {
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int i = 10;
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/// A loop that checks if the number is happy.
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while (i > 0) {
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int happy = solve(n);
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if (happy == 1) {
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return true;
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}
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n = happy;
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i--;
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}
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return false;
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}
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}
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```
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## SOlution 5
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```dart
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class Solution {
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// Runtime: 309 ms, faster than 100.00% of Dart online submissions for Happy Number.
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// Memory Usage: 158 MB, less than 7.32% of Dart online submissions for Happy Number.
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int sums(int n) {
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int ans = 0;
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while (n != 0) {
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//ans += pow(n % 10, 2);
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ans += pow(n % 10, 2).floor();
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n = n ~/ 10;
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}
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return ans;
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}
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bool isHappy(int n) {
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int s = sums(n);
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int f = sums(sums(n));
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if (f == 1) return true; //for case n==1
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while (s != f) {
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if (f == 1) return true;
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s = sums(s);
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f = sums(sums(f));
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}
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return false;
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}
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}
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```

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