add 3233

Author: fishercoder1534

Diff for: paginated_contents/algorithms/4th_thousand/README.md

@@ -1,5 +1,6 @@
 | #    | Title                                                                                                                                                               | Solutions                                                                                                                         | Video                                                                         | Difficulty | Tag                                                                  
 |------|---------------------------------------------------------------------------------------------------------------------------------------------------------------------|-----------------------------------------------------------------------------------------------------------------------------------|-------------------------------------------------------------------------------|------------|----------------------------------------------------------------------
+| 3233 | [Find the Count of Numbers Which Are Not Special](https://leetcode.com/problems/find-the-count-of-numbers-which-are-not-special/)                                                                 | [Java](https://github.com/fishercoder1534/Leetcode/blob/master/src/main/java/com/fishercoder/solutions/fourththousand/_3233.java) |                                                                               | Medium     | Math
 | 3232 | [Find if Digit Game Can Be Won](https://leetcode.com/problems/find-if-digit-game-can-be-won/)                                                                 | [Java](https://github.com/fishercoder1534/Leetcode/blob/master/src/main/java/com/fishercoder/solutions/fourththousand/_3232.java) |                                                                               | Easy       |
 | 3226 | [Number of Bit Changes to Make Two Integers Equal](https://leetcode.com/problems/number-of-bit-changes-to-make-two-integers-equal/)                                                                 | [Java](https://github.com/fishercoder1534/Leetcode/blob/master/src/main/java/com/fishercoder/solutions/fourththousand/_3226.java) |                                                                               | Easy       |
 | 3224 | [Minimum Array Changes to Make Differences Equal](https://leetcode.com/problems/minimum-array-changes-to-make-differences-equal/)                                                                 | [Java](https://github.com/fishercoder1534/Leetcode/blob/master/src/main/java/com/fishercoder/solutions/fourththousand/_3224.java) |                                                                               | Medium     |

Diff for: src/main/java/com/fishercoder/solutions/fourththousand/_3233.java

@@ -0,0 +1,49 @@
+package com.fishercoder.solutions.fourththousand;
+
+import java.util.Arrays;
+
+public class _3233 {
+    public static class Solution1 {
+        /**
+         * credit: https://leetcode.com/problems/find-the-count-of-numbers-which-are-not-special/solutions/5546339/sieve-of-eratosthenes/
+         * In order for a number to be special, it must be a square of a prime number;
+         * so we use sieve algorithm to find all prime numbers up to Math.sqrt(r);
+         * since Math.sqrt() method rounds down, we'll use Math.sqrt(r) + 1 as the bound for isPrime array
+         * and check if the number is within the range of [l, r] later.
+         */
+        public int nonSpecialCount(int l, int r) {
+            int limit = (int) Math.sqrt(r);
+            boolean[] isPrime = new boolean[limit + 1];
+            Arrays.fill(isPrime, true);
+            isPrime[0] = false;
+            isPrime[1] = false;
+            for (int i = 2; i * i < isPrime.length; i++) {
+                if (isPrime[i]) {
+                    //below for loop is key to construct isPrime[] array:
+                    //we start j from i * i, as long as j is within boundary, we increase j by i each time
+                    //i.e. if i = 2, j starts from 4, then 6, 8, 10, 12
+                    //if i = 3, j starts from 9, then 12, 15, 18, 21
+                    for (int j = i * i; j < isPrime.length; j += i) {
+                        isPrime[j] = false;
+                    }
+                }
+            }
+
+            //now count special numbers
+            int special = 0;
+            for (int i = Math.max(2, (int) Math.sqrt(l)); i < isPrime.length; i++) {
+                if (isPrime[i]) {
+                    int square = i * i;
+                    if (square <= r && square >= l) {
+                        special++;
+                    }
+                }
+            }
+            //total number of numbers in this range
+            int totalCount = r - l + 1;
+            //minus the special ones
+            return totalCount - special;
+        }
+
+    }
+}

Diff for: src/test/java/com/fishercoder/thirdthousand/_3233Test.java

@@ -0,0 +1,57 @@
+package com.fishercoder.thirdthousand;
+
+import com.fishercoder.solutions.fourththousand._3233;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+public class _3233Test {
+    private static _3233.Solution1 solution1;
+
+    @BeforeEach
+    public void setup() {
+        solution1 = new _3233.Solution1();
+    }
+
+    @Test
+    public void test1() {
+        assertEquals(3, solution1.nonSpecialCount(5, 7));
+    }
+
+    @Test
+    public void test2() {
+        assertEquals(11, solution1.nonSpecialCount(4, 16));
+    }
+
+    @Test
+    public void test3() {
+        assertEquals(14, solution1.nonSpecialCount(1, 16));
+    }
+
+    @Test
+    public void test4() {
+        assertEquals(2, solution1.nonSpecialCount(1, 2));
+    }
+
+    @Test
+    public void test5() {
+        assertEquals(3, solution1.nonSpecialCount(1, 3));
+    }
+
+    @Test
+    public void test6() {
+        assertEquals(3, solution1.nonSpecialCount(1, 4));
+    }
+
+    @Test
+    public void test7() {
+        assertEquals(77, solution1.nonSpecialCount(1, 81));
+    }
+
+    @Test
+    public void test8() {
+        assertEquals(433, solution1.nonSpecialCount(1, 441));
+    }
+
+}