add 1390

Author: fishercoder1534

README.md

@@ -8,6 +8,7 @@ _If you like this project, please leave me a star._ ★
 
 |  #  |      Title     |   Solutions   | Video  | Difficulty  | Tag                   
 |-----|----------------|---------------|--------|-------------|-------------
+|1390|[Four Divisors](https://leetcode.com/problems/four-divisors/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_1390.java) | |Medium|Math|
 |1389|[Create Target Array in the Given Order](https://leetcode.com/problems/create-target-array-in-the-given-order/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_1389.java) | |Easy|Array|
 |1388|[Pizza With 3n Slices](https://leetcode.com/problems/pizza-with-3n-slices/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_1388.java) | |Hard|DP|
 |1387|[Sort Integers by The Power Value](https://leetcode.com/problems/sort-integers-by-the-power-value/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_1387.java) | |Medium|Sort, Graph|

src/main/java/com/fishercoder/solutions/_1390.java

@@ -0,0 +1,53 @@
+package com.fishercoder.solutions;
+
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * 1390. Four Divisors
+ *
+ * Given an integer array nums, return the sum of divisors of the integers in that array that have exactly four divisors.
+ * If there is no such integer in the array, return 0.
+ *
+ * Example 1:
+ * Input: nums = [21,4,7]
+ * Output: 32
+ * Explanation:
+ * 21 has 4 divisors: 1, 3, 7, 21
+ * 4 has 3 divisors: 1, 2, 4
+ * 7 has 2 divisors: 1, 7
+ * The answer is the sum of divisors of 21 only.
+ *
+ * Constraints:
+ * 1 <= nums.length <= 10^4
+ * 1 <= nums[i] <= 10^5
+ * */
+public class _1390 {
+    public static class Solution1 {
+        public int sumFourDivisors(int[] nums) {
+            int sum = 0;
+            for (int i = 0; i < nums.length; i++) {
+                List<Integer> divisors = getDivisors(nums[i]);
+                if (divisors.size() == 4) {
+                    for (int div : divisors) {
+                        sum += div;
+                    }
+                }
+            }
+            return sum;
+        }
+
+        private List<Integer> getDivisors(int num) {
+            List<Integer> divisors = new ArrayList<>();
+            for (int i = 1; i <= Math.sqrt(num); ++i) {
+                if (num % i == 0) {
+                    divisors.add(i);
+                    if (num / i != i) {
+                        divisors.add(num / i);
+                    }
+                }
+            }
+            return divisors;
+        }
+    }
+}

src/test/java/com/fishercoder/_1390Test.java

@@ -0,0 +1,22 @@
+package com.fishercoder;
+
+import com.fishercoder.solutions._1390;
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+import static org.junit.Assert.assertEquals;
+
+public class _1390Test {
+    private static _1390.Solution1 solution1;
+
+    @BeforeClass
+    public static void setup() {
+        solution1 = new _1390.Solution1();
+    }
+
+    @Test
+    public void test1() {
+        assertEquals(32, solution1.sumFourDivisors(new int[]{21, 4, 7}));
+    }
+
+}