Add solution #79

Author: JoshCrozier

README.md

@@ -83,6 +83,7 @@
 75|[Sort Colors](./0075-sort-colors.js)|Medium|
 77|[Combinations](./0077-combinations.js)|Medium|
 78|[Subsets](./0078-subsets.js)|Medium|
+79|[Word Search](./0079-word-search.js)|Medium|
 80|[Remove Duplicates from Sorted Array II](./0080-remove-duplicates-from-sorted-array-ii.js)|Medium|
 81|[Search in Rotated Sorted Array II](./0081-search-in-rotated-sorted-array-ii.js)|Medium|
 82|[Remove Duplicates from Sorted List II](./0082-remove-duplicates-from-sorted-list-ii.js)|Medium|

solutions/0079-word-search.js

@@ -0,0 +1,52 @@
+/**
+ * 79. Word Search
+ * https://leetcode.com/problems/word-search/
+ * Difficulty: Medium
+ *
+ * Given an m x n grid of characters board and a string word, return true if word exists
+ * in the grid.
+ *
+ * The word can be constructed from letters of sequentially adjacent cells, where adjacent
+ * cells are horizontally or vertically neighboring. The same letter cell may not be used
+ * more than once.
+ */
+
+/**
+ * @param {character[][]} board
+ * @param {string} word
+ * @return {boolean}
+ */
+var exist = function(board, word) {
+  function backtrack(x, y, k) {
+    if (board[x][y] !== word[k]) {
+      return false;
+    } else if (k === word.length - 1) {
+      return true;
+    }
+
+    board[x][y] = '-';
+
+    for (const direction of [[-1, 0], [0, 1], [1, 0], [0, -1]]) {
+      const [i, j] = [x + direction[0], y + direction[1]];
+      if (i >= 0 && i < board.length && j >= 0 && j < board[0].length) {
+        if (backtrack(i, j, k + 1)) {
+          return true;
+        }
+      }
+    }
+
+    board[x][y] = word[k];
+
+    return false;
+  }
+
+  for (let i = 0; i < board.length; i++) {
+    for (let j = 0; j < board[0].length; j++) {
+      if (backtrack(i, j, 0)) {
+        return true;
+      }
+    }
+  }
+
+  return false;
+};