Create 442_Find_All_Duplicates_in_an_Array.java (qiyuangong#81)

Contributed by @ajay2614

Author: ajay2614

java/442_Find_All_Duplicates_in_an_Array.java

@@ -0,0 +1,17 @@
+class Solution {
+    public List<Integer> findDuplicates(int[] nums) {
+        int n = nums.length;
+
+        List<Integer> ans = new ArrayList<>();
+
+        for(int i=0;i<n;i++) {
+            int possibleVal = Math.abs(nums[i]);
+
+            if(nums[possibleVal - 1] < 0) {
+                ans.add(possibleVal);
+            }
+            nums[possibleVal - 1] = -1 * nums[possibleVal - 1];
+        }
+        return ans;
+    }
+}