Array-2 completed

findDisappearedNumbers.java

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+// Time Complexity :
+// Space Complexity :
+// Did this code successfully run on Leetcode :
+// Any problem you faced while coding this :
+
+// Question https://leetcode.com/problems/find-all-numbers-disappeared-in-an-array/
+// Your code here along with comments explaining your approach
+/**
+ * Time complexity : O(n) where n is number of elements in array
+ * Space complexity : O(n)
+ * Did this code successfully run on Leetcode : yes
+ */
+class Solution {
+    public List<Integer> findDisappearedNumbers(int[] nums) {
+      HashMap<Integer,Boolean> map = new HashMap<>();
+      // Iterate over array nums and store in map to show its presence by marking as true
+      for(int i=0;i<nums.length;++i){
+         map.put(nums[i],true);
+      }
+      List<Integer> result = new ArrayList<>();
+      for(int i=1;i<=nums.length;++i){
+        // if map does not contain any value from array it means it is not present in array
+         if(!map.containsKey(i)){
+            result.add(i);
+         }
+      }
+      return result;
+    }
+}
+/**
+ * Time complexity : O(n)
+ * Space complexity : O(1)
+ * Did this code successfully run on Leetcode : yes
+ * 
+ */
+class Solution {
+    public List<Integer> findDisappearedNumbers(int[] nums) {
+        for(int i=0;i<nums.length;++i){
+            // converting the values as negative by taking num[i]-1 as index value in same array
+            int idx = Math.abs(nums[i])-1;
+            if(nums[idx]>0){
+              nums[idx] = - nums[idx];
+           }
+        }
+        List<Integer> result = new ArrayList<>();
+        for(int i=0;i<nums.length;++i){
+            // if any number is not converted into negative it means those are not present
+            if(nums[i]>0){
+                result.add(i+1);
+            }
+        }
+        return result;
+    }
+}

gameOfLife.java

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+// Question https://leetcode.com/problems/game-of-life/
+/**
+ * Time complexity : O(n*m)
+ * Space complexity : O(1)
+ * Did this code successfully run on Leetcode : yes
+ */
+class Solution {
+    // 0->1 
+    int[][] dirs;
+    public void gameOfLife(int[][] board) {
+        this.dirs = new int[][]{{-1,0},{1,0},{0,-1},{0,1},{-1,-1},{-1,1},{1,-1},{1,1}};
+        int m = board.length;
+        int n = board[0].length;
+        for(int i=0;i<m;++i){
+            for(int j=0;j<n;++j){
+                // get the count of live cells
+              int alive = countOfliveCells(board,i,j);  
+
+              if(board[i][j]==0 && alive==3){
+                 board[i][j] = 3; // dead will convert into alive
+              }else if(board[i][j]==1 && (alive<2 || alive>3)){
+                 board[i][j] = 2; // alive will convert into dead
+              }  
+            }
+        }
+        for(int i=0;i<m;++i){
+            for(int j=0;j<n;++j){
+                if(board[i][j]==2){
+                    board[i][j] = 0;
+                }else if(board[i][j]==3){
+                     board[i][j] = 1;
+                }
+            }
+        }
+    }
+    int countOfliveCells(int[][] board,int i,int j){
+        int count = 0;
+        for(int[] dir: dirs){
+            int nr = i+dir[0];
+            int nc = j+dir[1];
+            if((nr>=0 && nr<board.length) && (nc>=0 && nc<board[0].length)){
+                if(board[nr][nc]==1 || board[nr][nc]==2) count++;
+            }
+        }
+        return count;
+    }
+}