Add solution #861

Author: JoshCrozier

README.md

@@ -668,6 +668,7 @@
 858|[Mirror Reflection](./0858-mirror-reflection.js)|Medium|
 859|[Buddy Strings](./0859-buddy-strings.js)|Easy|
 860|[Lemonade Change](./0860-lemonade-change.js)|Easy|
+861|[Score After Flipping Matrix](./0861-score-after-flipping-matrix.js)|Medium|
 867|[Transpose Matrix](./0867-transpose-matrix.js)|Easy|
 868|[Binary Gap](./0868-binary-gap.js)|Easy|
 872|[Leaf-Similar Trees](./0872-leaf-similar-trees.js)|Easy|

solutions/0861-score-after-flipping-matrix.js

@@ -0,0 +1,45 @@
+/**
+ * 861. Score After Flipping Matrix
+ * https://leetcode.com/problems/score-after-flipping-matrix/
+ * Difficulty: Medium
+ *
+ * You are given an m x n binary matrix grid.
+ *
+ * A move consists of choosing any row or column and toggling each value in that row or
+ * column (i.e., changing all 0's to 1's, and all 1's to 0's).
+ *
+ * Every row of the matrix is interpreted as a binary number, and the score of the matrix
+ * is the sum of these numbers.
+ *
+ * Return the highest possible score after making any number of moves (including zero moves).
+ */
+
+/**
+ * @param {number[][]} grid
+ * @return {number}
+ */
+var matrixScore = function(grid) {
+  const rows = grid.length;
+  const cols = grid[0].length;
+
+  for (let row = 0; row < rows; row++) {
+    if (grid[row][0] === 0) {
+      for (let col = 0; col < cols; col++) {
+        grid[row][col] ^= 1;
+      }
+    }
+  }
+
+  let result = rows * (1 << (cols - 1));
+
+  for (let col = 1; col < cols; col++) {
+    let onesCount = 0;
+    for (let row = 0; row < rows; row++) {
+      onesCount += grid[row][col];
+    }
+    const maxOnes = Math.max(onesCount, rows - onesCount);
+    result += maxOnes * (1 << (cols - 1 - col));
+  }
+
+  return result;
+};