add 3239

Author: fishercoder1534

Diff for: paginated_contents/algorithms/4th_thousand/README.md

@@ -1,5 +1,6 @@
 | #    | Title                                                                                                                                                               | Solutions                                                                                                                         | Video                                                                         | Difficulty | Tag                                                                  
 |------|---------------------------------------------------------------------------------------------------------------------------------------------------------------------|-----------------------------------------------------------------------------------------------------------------------------------|-------------------------------------------------------------------------------|------------|----------------------------------------------------------------------
+| 3239 | [Minimum Number of Flips to Make Binary Grid Palindromic I](https://leetcode.com/problems/minimum-number-of-flips-to-make-binary-grid-palindromic-i/)                                                                 | [Java](https://github.com/fishercoder1534/Leetcode/blob/master/src/main/java/com/fishercoder/solutions/fourththousand/_3239.java) |                                                                               | Easy       |
 | 3238 | [Find the Number of Winning Players](https://leetcode.com/problems/find-the-number-of-winning-players/)                                                                 | [Java](https://github.com/fishercoder1534/Leetcode/blob/master/src/main/java/com/fishercoder/solutions/fourththousand/_3238.java) |                                                                               | Easy       |
 | 3237 | [Alt and Tab Simulation](https://leetcode.com/problems/alt-and-tab-simulation/)                                                                 | [Java](https://github.com/fishercoder1534/Leetcode/blob/master/src/main/java/com/fishercoder/solutions/fourththousand/_3237.java) |                                                                               | Medium     | 
 | 3234 | [Count the Number of Substrings With Dominant Ones](https://leetcode.com/problems/count-the-number-of-substrings-with-dominant-ones/)                                                                 | [Java](https://github.com/fishercoder1534/Leetcode/blob/master/src/main/java/com/fishercoder/solutions/fourththousand/_3234.java) |                                                                               | Medium     | Sliding Window

Diff for: src/main/java/com/fishercoder/solutions/fourththousand/_3239.java

@@ -0,0 +1,32 @@
+package com.fishercoder.solutions.fourththousand;
+
+public class _3239 {
+    public static class Solution1 {
+        public int minFlips(int[][] grid) {
+            int m = grid.length;
+            int n = grid[0].length;
+            int ans = m * n;
+            //try rows first
+            int flips = 0;
+            for (int i = 0; i < m; i++) {
+                for (int left = 0, right = n - 1; left < right; left++, right--) {
+                    if (grid[i][left] != grid[i][right]) {
+                        flips++;
+                    }
+                }
+            }
+            ans = Math.min(ans, flips);
+            flips = 0;
+            //try columns now
+            for (int j = 0; j < n; j++) {
+                for (int top = 0, bottom = m - 1; top < bottom; top++, bottom--) {
+                    if (grid[top][j] != grid[bottom][j]) {
+                        flips++;
+                    }
+                }
+            }
+            ans = Math.min(flips, ans);
+            return ans;
+        }
+    }
+}