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fishercoder1534fishercoder1534
committedJul 14, 2024·
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  • paginated_contents/algorithms/1st_thousand
  • src
    • main/java/com/fishercoder/solutions/firstthousand
    • test/java/com/fishercoder/firstthousand

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‎paginated_contents/algorithms/1st_thousand/README.md

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| 729 | [My Calendar I](https://leetcode.com/problems/my-calendar-i/) | [Solution](https://github.com/fishercoder1534/Leetcode/blob/master/src/main/java/com/fishercoder/solutions/firstthousand/_729.java) || Medium |
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| 728 | [Self Dividing Numbers](https://leetcode.com/problems/self-dividing-numbers/) | [Solution](https://github.com/fishercoder1534/Leetcode/blob/master/src/main/java/com/fishercoder/solutions/firstthousand/_728.java) | | Easy |
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| 727 | [Minimum Window Subsequence](https://leetcode.com/problems/minimum-window-subsequence/) | [Solution](https://github.com/fishercoder1534/Leetcode/blob/master/src/main/java/com/fishercoder/solutions/firstthousand/_727.java) | | Hard | DP
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| 726 | [Number of Atoms](https://leetcode.com/problems/number-of-atoms/) | [Solution](https://github.com/fishercoder1534/Leetcode/blob/master/src/main/java/com/fishercoder/solutions/firstthousand/_726.java) | | Hard | Stack
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| 725 | [Split Linked List in Parts](https://leetcode.com/problems/split-linked-list-in-parts/) | [Solution](https://github.com/fishercoder1534/Leetcode/blob/master/src/main/java/com/fishercoder/solutions/firstthousand/_725.java) | | Medium | LinkedList
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| 724 | [Find Pivot Index](https://leetcode.com/problems/find-pivot-index/) | [Solution](https://github.com/fishercoder1534/Leetcode/blob/master/src/main/java/com/fishercoder/solutions/firstthousand/_724.java) | | Easy | Array
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| 723 | [Candy Crush](https://leetcode.com/problems/candy-crush/) | [Solution](https://github.com/fishercoder1534/Leetcode/blob/master/src/main/java/com/fishercoder/solutions/firstthousand/_723.java) | | Medium | Array, Two Pointers

‎src/main/java/com/fishercoder/solutions/firstthousand/_726.java

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package com.fishercoder.solutions.firstthousand;
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import java.util.ArrayList;
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import java.util.Collections;
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import java.util.Deque;
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import java.util.HashMap;
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import java.util.LinkedList;
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import java.util.List;
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import java.util.Map;
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public class _726 {
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public static class Solution1 {
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/**
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* My completely original solution:
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* 1. use a stack;
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* 2. whenever we encounter the open paren, we push it into the top of the stack;
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* 3. whenever we encounter an uppercase, we check to get its full atom letters,
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* then check to get the number after it if there's any, then form a pair objet and push onto the stack;
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* 4. whenever we encounter the closed paren, we check if there's any number after it,
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* then poll all items on top of the stack off onto a new/temp stack until we encounter the corresponding open paren,
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* then add these items from the temp stack back into the original/main stack;
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*/
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public String countOfAtoms(String formula) {
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Deque<Pair> stack = new LinkedList<>();
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for (int i = 0; i < formula.length(); i++) {
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char curr = formula.charAt(i);
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if (curr == '(') {
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stack.addLast(new Pair("(", 1));
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} else if (Character.isUpperCase(curr)) {
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StringBuilder sb = new StringBuilder(curr + "");
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i++;
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while (i < formula.length() && Character.isLowerCase(formula.charAt(i))) {
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sb.append(formula.charAt(i++));
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}
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if (i < formula.length()) {
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if (Character.isUpperCase(formula.charAt(i)) || formula.charAt(i) == '(' || formula.charAt(i) == ')') {
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//no numbers
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stack.addLast(new Pair(sb.toString(), 1));
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i--;
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} else {
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//there are numbers
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StringBuilder numberSb = new StringBuilder();
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while (i < formula.length() && Character.isDigit(formula.charAt(i))) {
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numberSb.append(formula.charAt(i++));
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}
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i--;
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stack.addLast(new Pair(sb.toString(), Integer.parseInt(numberSb.toString())));
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}
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} else {
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stack.addLast(new Pair(sb.toString(), 1));
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}
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} else if (curr == ')') {
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i++;
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StringBuilder sb = new StringBuilder();
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while (i < formula.length() && Character.isDigit(formula.charAt(i))) {
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sb.append(formula.charAt(i));
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i++;
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}
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i--;
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int number = 1;
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if (sb.length() > 0) {
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number = Integer.parseInt(sb.toString());
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}
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Deque<Pair> stack2 = new LinkedList<>();
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while (!stack.isEmpty() && !stack.peekLast().atom.equals("(")) {
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Pair pair = stack.pollLast();
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stack2.addLast(new Pair(pair.atom, pair.count * number));
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}
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stack.pollLast();//poll "(" off of the stack
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while (!stack2.isEmpty()) {
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stack.addLast(stack2.pollLast());
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}
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}
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}
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List<Pair> list = new ArrayList<>();
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while (!stack.isEmpty()) {
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list.add(stack.pollLast());
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}
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//now merge the same atoms
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Map<String, Integer> map = new HashMap<>();
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for (Pair pair : list) {
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map.put(pair.atom, map.getOrDefault(pair.atom, 0) + pair.count);
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}
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//now add the merged atoms into the list again before sorting them
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list.clear();
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for (Map.Entry<String, Integer> entry : map.entrySet()) {
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list.add(new Pair(entry.getKey(), entry.getValue()));
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}
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Collections.sort(list, (a, b) -> a.atom.compareToIgnoreCase(b.atom));
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StringBuilder sb = new StringBuilder();
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for (Pair pair : list) {
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sb.append(pair.atom + (pair.count == 1 ? "" : pair.count));
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}
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return sb.toString();
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}
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class Pair {
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String atom;
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int count;
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public Pair(String atom, int count) {
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this.atom = atom;
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this.count = count;
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}
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}
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}
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}

‎src/test/java/com/fishercoder/firstthousand/_726Test.java

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package com.fishercoder.firstthousand;
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import com.fishercoder.solutions.firstthousand._726;
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import org.junit.jupiter.api.BeforeEach;
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import org.junit.jupiter.api.Test;
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import static org.junit.jupiter.api.Assertions.assertEquals;
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public class _726Test {
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private static _726.Solution1 solution1;
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@BeforeEach
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public void setup() {
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solution1 = new _726.Solution1();
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}
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@Test
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public void test1() {
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assertEquals("H2O", solution1.countOfAtoms("H2O"));
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}
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@Test
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public void test2() {
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assertEquals("H2MgO2", solution1.countOfAtoms("Mg(OH)2"));
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}
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@Test
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public void test3() {
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assertEquals("K4N2O14S4", solution1.countOfAtoms("K4(ON(SO3)2)2"));
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}
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@Test
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public void test4() {
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assertEquals("H2MgNO", solution1.countOfAtoms("Mg(H2O)N"));
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}
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}

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