diff --git a/Leetcode_289.java b/Leetcode_289.java
new file mode 100644
index 00000000..bdfa7864
--- /dev/null
+++ b/Leetcode_289.java
@@ -0,0 +1,64 @@
+//In this problem, we need to update the given board. If we do so, we might loose old value. To retain it, we will update the values other than 0 or 1[as 0 and 1 are given in input]
+//TC: 8*O(m*n); SC:O(1)
+
+
+class Solution {
+    public void gameOfLife(int[][] board) {
+
+        int n=board.length;
+        int m=board[0].length;
+
+        for(int i=0;i<n;i++){
+            for(int j=0;j<m;j++){
+                int active=getAliveCount(board,i,j);
+
+                if(board[i][j] == 1 && (active>3 || active<2)){
+                    board[i][j]=2;
+                }
+
+                if(board[i][j] == 0 && (active==3)){
+                    board[i][j]=3;
+                } 
+
+
+            }
+        }
+
+        for(int i=0;i<n;i++){
+            for(int j=0;j<m;j++){
+                if(board[i][j]==2){
+                    board[i][j]=0;
+                }
+
+                if(board[i][j]==3){
+                    board[i][j]=1;
+                }
+            }
+        }
+        
+    }
+
+    private int getAliveCount(int[][] board, int i, int j){
+        int[][] dir=new int[][]{
+            {-1,-1},{0,-1},{-1,0},{1,1},{0,1},{1,0},{-1,1},{1,-1}
+        };
+
+        int ans=0;
+
+        for(int[] d:dir){
+            int r=i+d[0];
+            int c=j+d[1];
+
+            if((r>=0 && r<board.length) && (c>=0 && c<board[0].length)){
+                if(board[r][c]==1 || board[r][c]==2){
+                ans+=1;
+            }
+
+            }
+            
+
+        }
+
+        return ans;
+    }
+}
diff --git a/Leetcode_448.java b/Leetcode_448.java
new file mode 100644
index 00000000..5174ec19
--- /dev/null
+++ b/Leetcode_448.java
@@ -0,0 +1,58 @@
+//way1
+//Store them in Set. Iterate and identify which element is missed.
+//TC: O(2n); SC: O(n)
+class Solution {
+    public List<Integer> findDisappearedNumbers(int[] nums) {
+        Set<Integer> set=new HashSet<>();
+
+        //first iteration
+        for(int i:nums){
+            set.add(i);
+        }
+
+        int n=nums.length;
+
+        List<Integer> ans=new ArrayList<>();
+        //second iteration
+        for(int i=1;i<=n;i++){
+            if(!(set.contains(i))){
+                ans.add(i);
+            }
+        }
+
+        return ans;
+        
+    }
+}
+
+//way2
+//Mutate the original array by going to the exact position of element present at index
+//nums[0]=5 -- go to index 4[because 5th element's position is at 4] and update it to negative value at 4th index. It means element 5 is present
+//After updating the entire array with abive concept, travel array again to identify missing elements
+//TC: O(2n); SC: constant
+class Solution {
+    public List<Integer> findDisappearedNumbers(int[] nums) {
+        int n=nums.length;
+        for(int i=0;i<n;i++){
+            int idx=Math.abs(nums[i])-1;
+            if(nums[idx]>0){
+                nums[idx]*=-1;
+            }
+
+        }
+
+        List<Integer> ans=new ArrayList<>();
+
+        for(int i=0;i<n;i++){
+            
+            if(nums[i]>0){
+                ans.add(i+1);
+            }else{
+                nums[i]*=-1;
+            }
+        }
+
+        return ans;
+        
+    }
+}