Find All Numbers Disappeared in an Array, Min and Max in Array and Game of Life

Problem1.cs

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+// Time Complexity : O(n) where n is the total length of nums array
+// Space Complexity : O(1)
+// Did this code successfully run on Leetcode : Yes
+// Any problem you faced while coding this : No
+
+public class Solution {
+    public IList<int> FindDisappearedNumbers(int[] nums) {
+        List<int> result = new();
+
+        for(int i = 0; i < nums.Length; i++)
+        {
+            int index = Math.Abs(nums[i]) - 1;
+
+            if(nums[index] > 0) 
+            {
+                nums[index] *= -1;
+            }
+        }
+
+        for(int i = 0; i < nums.Length; i++)
+        {
+            if(nums[i] > 0)
+            {
+                result.Add(i+1);
+            }
+        }
+
+        return result;
+    }
+}

Problem2.cs

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+// Time Complexity : O(n) where n is the length of arr
+// Space Complexity : O(1)
+// Did this code successfully run on Leetcode : Yes
+// Any problem you faced while coding this : No
+
+public class Solution {
+    public List<int> getMinMax(int[] arr) {
+        // code here
+        List<int> result = new();
+        int min = 0, max = 0;
+        int i;
+
+        if(arr.Length % 2 != 0)
+        {
+            min = arr[0];
+            max = arr[0];
+            i=1;
+        }
+
+        else
+        {
+            min = Math.Min(arr[0], arr[1]);
+            max = Math.Max(arr[0], arr[1]);
+            i=2;
+        }
+
+
+        while(i<arr.Length)
+        {
+            if(arr[i] < arr[i+1])
+            {
+                min = Math.Min(arr[i], min);
+                max = Math.Max(arr[i+1], max);
+            }
+
+            else
+            {
+                min = Math.Min(arr[i+1], min);
+                max = Math.Max(arr[i], max);
+            }
+
+            i+=2;
+        }
+
+        result.Add(min);
+        result.Add(max);
+        return result;
+    }
+}

Problem3.cs

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+// Time Complexity : O(m*n) where m & n are the dimensions of board
+// Space Complexity : O(1)
+// Did this code successfully run on Leetcode : Yes
+// Any problem you faced while coding this : No
+public class Solution {
+    private int rows;
+    private int columns;
+    private int[][] dirs;
+    public void GameOfLife(int[][] board) {
+        rows = board.Length;
+        columns = board[0].Length;
+        dirs = new int[][]
+        {
+            new int[] {0,1},
+            new int[] {0,-1},
+            new int[] {1,0},
+            new int[] {-1,0},
+            new int[] {-1,-1},
+            new int[] {1,1},
+            new int[] {-1,1},
+            new int[] {1,-1},
+        };
+
+        Helper(board);
+
+        for(int i = 0; i < rows; i++)
+        {
+            for(int j = 0; j < columns; j++)
+            {
+                // 1 -> 0 : 2
+                if(board[i][j] == 2)
+                {
+                    board[i][j] = 0;
+                }
+
+                // 0 -> 1 : 3
+                else if(board[i][j] == 3)
+                {
+                    board[i][j] = 1;
+                }
+            }
+        }
+    }
+
+    public void Helper(int[][] board)
+    {
+        for(int i = 0; i < rows; i++)
+        {
+            for(int j = 0; j < columns; j++)
+            {
+                int neighbours = GetNeighbours(board, i , j);
+
+                if(board[i][j] == 1)
+                {
+                    if(neighbours < 2 || neighbours > 3)
+                    {
+                        board[i][j] = 2;
+                    }
+                }
+
+                else if(board[i][j] == 0)
+                {
+                    if(neighbours == 3)
+                    {
+                        board[i][j] = 3;
+                    }
+                }
+            }
+        }
+    }
+
+    public int GetNeighbours(int[][] board, int i, int j)
+    {
+        int neighbours = 0;
+
+        foreach(int[] dir in dirs)
+        {
+            int nr = i + dir[0];
+            int nc = j + dir[1];
+            if(nr>=0 && nr<rows && nc>=0 && nc<columns && (board[nr][nc] == 1 || board[nr][nc] == 2))
+            {
+                neighbours += 1;
+            }
+        }
+
+        return neighbours;
+    }
+}