solve problem Find All Duplicates In An Array

Author: P-ppc

README.md

@@ -241,6 +241,7 @@ All solutions will be accepted!
 |284|[Peeking Iterator](https://leetcode-cn.com/problems/peeking-iterator/description/)|[java/py](./algorithms/PeekingIterator)|Medium|
 |328|[Odd Even Linked List](https://leetcode-cn.com/problems/odd-even-linked-list/description/)|[java/py/js](./algorithms/OddEvenLinkedList)|Medium|
 |677|[Map Sum Pairs](https://leetcode-cn.com/problems/map-sum-pairs/description/)|[java/py/js](./algorithms/MapSumPairs)|Medium|
+|442|[Find All Duplicates In An Array](https://leetcode-cn.com/problems/find-all-duplicates-in-an-array/description/)|[java/py/js](./algorithms/FindAllDuplicatesInAnArray)|Medium|
 
 # Database
 |#|Title|Solution|Difficulty|

algorithms/FindAllDuplicatesInAnArray/README.md

@@ -0,0 +1,2 @@
+# Find All Duplicates In An Array
+This problem is easy to solve

algorithms/FindAllDuplicatesInAnArray/Solution.java

@@ -0,0 +1,15 @@
+class Solution {
+    public List<Integer> findDuplicates(int[] nums) {
+        List<Integer> res = new ArrayList<Integer>();
+        
+        for (int num : nums) {
+            num = Math.abs(num);
+            if (nums[num - 1] < 0) {
+                res.add(num);
+            } else {
+                nums[num - 1] *= -1;
+            }
+        }
+        return res;
+    }
+}

algorithms/FindAllDuplicatesInAnArray/solution.js

@@ -0,0 +1,18 @@
+/**
+ * @param {number[]} nums
+ * @return {number[]}
+ */
+var findDuplicates = function(nums) {
+    let res = []
+    
+    nums.forEach(num => {
+        num = Math.abs(num)
+        if (nums[num - 1] < 0) {
+            res.push(num)
+        } else {
+            nums[num - 1] *= -1
+        }
+    })
+    
+    return res
+};

algorithms/FindAllDuplicatesInAnArray/solution.py

@@ -0,0 +1,15 @@
+class Solution(object):
+    def findDuplicates(self, nums):
+        """
+        :type nums: List[int]
+        :rtype: List[int]
+        """
+        res = []
+        for num in nums:
+            num = abs(num)
+            if nums[num - 1] < 0:
+                res.append(num)
+            else:
+                nums[num - 1] *= -1
+                
+        return res