diff --git a/leetcode/array/ContainsDuplicatesII.java b/leetcode/array/ContainsDuplicatesII.java
index 81240ea2..597acf58 100644
--- a/leetcode/array/ContainsDuplicatesII.java
+++ b/leetcode/array/ContainsDuplicatesII.java
@@ -1,6 +1,11 @@
 //Given an array of integers and an integer k, find out whether there are two distinct indices i and 
 //j in the array such that nums[i] = nums[j] and the absolute difference between i and j is at most k.
 
+//Example
+
+// [2,5,-1,6,-9,5,8]. k=3, i=1, j= 5 |i-j|=4 4>3 --> false
+// [2,3,-1,3,-9,5,8]. k=3, i=1, j= 3 |i-j|=2 2<3 --> true
+
 class ContainsDuplicatesII {
     public boolean containsNearbyDuplicate(int[] nums, int k) {
         HashMap<Integer, Integer> map = new HashMap<Integer, Integer>();
diff --git a/leetcode/array/FindAllNumbersDisappearedInAnArray.java b/leetcode/array/FindAllNumbersDisappearedInAnArray.java
index c9ca7780..e79ff356 100644
--- a/leetcode/array/FindAllNumbersDisappearedInAnArray.java
+++ b/leetcode/array/FindAllNumbersDisappearedInAnArray.java
@@ -14,24 +14,19 @@
 
 class FindAllNumbersDisappearedInAnArray {
     public List<Integer> findDisappearedNumbers(int[] nums) {
-        List<Integer> result = new ArrayList<Integer>();
-        HashMap<Integer, Integer> map = new HashMap<Integer, Integer>();
-        for(int i = 1; i <= nums.length; i++) {
-            map.put(i, 1);
-        }
-        
-        for(int i = 0; i < nums.length; i++) {
-            if(map.containsKey(nums[i])) {
-                map.put(nums[i], -1);
-            }
-        }
-        
-        for(int i: map.keySet()) {
-            if(map.get(i) != -1) {
-                result.add(i);
+         List<Integer> result = new ArrayList<>();
+        for (int i = 0; i < ary.length; i++) {
+            if (ary[i] < i + 1) {
+                result.add(i + 1);
+            } else if (ary[i] > i + 1 && ary[ary[i] - 1]!=ary[i]) {
+                int temp = ary[ary[i] - 1];
+                ary[ary[i] - 1] = ary[i];
+                ary[i] = temp;
+                i--;
+            } else if (ary[i]!=i+1) {
+                result.add(i + 1);
             }
         }
-        
         return result;
     }
 }