Add solution #782

Author: JoshCrozier

README.md

@@ -592,6 +592,7 @@
 779|[K-th Symbol in Grammar](./0779-k-th-symbol-in-grammar.js)|Medium|
 780|[Reaching Points](./0780-reaching-points.js)|Hard|
 781|[Rabbits in Forest](./0781-rabbits-in-forest.js)|Medium|
+782|[Transform to Chessboard](./0782-transform-to-chessboard.js)|Hard|
 783|[Minimum Distance Between BST Nodes](./0783-minimum-distance-between-bst-nodes.js)|Easy|
 784|[Letter Case Permutation](./0784-letter-case-permutation.js)|Medium|
 790|[Domino and Tromino Tiling](./0790-domino-and-tromino-tiling.js)|Medium|

solutions/0782-transform-to-chessboard.js

@@ -0,0 +1,55 @@
+/**
+ * 782. Transform to Chessboard
+ * https://leetcode.com/problems/transform-to-chessboard/
+ * Difficulty: Hard
+ *
+ * You are given an n x n binary grid board. In each move, you can swap any two rows with each
+ * other, or any two columns with each other.
+ *
+ * Return the minimum number of moves to transform the board into a chessboard board. If the
+ * task is impossible, return -1.
+ *
+ * A chessboard board is a board where no 0's and no 1's are 4-directionally adjacent.
+ */
+
+/**
+ * @param {number[][]} board
+ * @return {number}
+ */
+var movesToChessboard = function(board) {
+  const n = board.length;
+
+  for (let i = 0; i < n; i++) {
+    for (let j = 0; j < n; j++) {
+      if ((board[0][0] ^ board[i][0] ^ board[0][j] ^ board[i][j]) === 1) {
+        return -1;
+      }
+    }
+  }
+
+  let rowSum = 0;
+  let colSum = 0;
+  let rowSwaps = 0;
+  let colSwaps = 0;
+
+  for (let i = 0; i < n; i++) {
+    rowSum += board[0][i];
+    colSum += board[i][0];
+
+    if (board[i][0] === i % 2) rowSwaps++;
+    if (board[0][i] === i % 2) colSwaps++;
+  }
+
+  if (rowSum !== Math.floor(n / 2) && rowSum !== Math.ceil(n / 2)) return -1;
+  if (colSum !== Math.floor(n / 2) && colSum !== Math.ceil(n / 2)) return -1;
+
+  if (n % 2 === 1) {
+    if (rowSwaps % 2 === 1) rowSwaps = n - rowSwaps;
+    if (colSwaps % 2 === 1) colSwaps = n - colSwaps;
+  } else {
+    rowSwaps = Math.min(rowSwaps, n - rowSwaps);
+    colSwaps = Math.min(colSwaps, n - colSwaps);
+  }
+
+  return Math.floor((rowSwaps + colSwaps) / 2);
+};