Add solution #1391

Author: JoshCrozier

README.md

@@ -1,4 +1,4 @@
-# 1,274 LeetCode solutions in JavaScript
+# 1,275 LeetCode solutions in JavaScript
 
 [https://leetcodejavascript.com](https://leetcodejavascript.com)
 
@@ -1061,6 +1061,7 @@
 1388|[Pizza With 3n Slices](./solutions/1388-pizza-with-3n-slices.js)|Hard|
 1389|[Create Target Array in the Given Order](./solutions/1389-create-target-array-in-the-given-order.js)|Easy|
 1390|[Four Divisors](./solutions/1390-four-divisors.js)|Medium|
+1391|[Check if There is a Valid Path in a Grid](./solutions/1391-check-if-there-is-a-valid-path-in-a-grid.js)|Medium|
 1400|[Construct K Palindrome Strings](./solutions/1400-construct-k-palindrome-strings.js)|Medium|
 1402|[Reducing Dishes](./solutions/1402-reducing-dishes.js)|Hard|
 1408|[String Matching in an Array](./solutions/1408-string-matching-in-an-array.js)|Easy|

solutions/1391-check-if-there-is-a-valid-path-in-a-grid.js

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+/**
+ * 1391. Check if There is a Valid Path in a Grid
+ * https://leetcode.com/problems/check-if-there-is-a-valid-path-in-a-grid/
+ * Difficulty: Medium
+ *
+ * You are given an m x n grid. Each cell of grid represents a street. The street of grid[i][j]
+ * can be:
+ * - 1 which means a street connecting the left cell and the right cell.
+ * - 2 which means a street connecting the upper cell and the lower cell.
+ * - 3 which means a street connecting the left cell and the lower cell.
+ * - 4 which means a street connecting the right cell and the lower cell.
+ * - 5 which means a street connecting the left cell and the upper cell.
+ * - 6 which means a street connecting the right cell and the upper cell.
+ *
+ * You will initially start at the street of the upper-left cell (0, 0). A valid path in the
+ * grid is a path that starts from the upper left cell (0, 0) and ends at the bottom-right
+ * cell (m - 1, n - 1). The path should only follow the streets.
+ *
+ * Notice that you are not allowed to change any street.
+ *
+ * Return true if there is a valid path in the grid or false otherwise.
+ */
+
+/**
+ * @param {number[][]} grid
+ * @return {boolean}
+ */
+var hasValidPath = function(grid) {
+  const rows = grid.length;
+  const cols = grid[0].length;
+  const directions = {
+    1: [[0, -1, [1, 4, 6]], [0, 1, [1, 3, 5]]],
+    2: [[-1, 0, [2, 3, 4]], [1, 0, [2, 5, 6]]],
+    3: [[0, -1, [1, 4, 6]], [1, 0, [2, 5, 6]]],
+    4: [[0, 1, [1, 3, 5]], [1, 0, [2, 5, 6]]],
+    5: [[0, -1, [1, 4, 6]], [-1, 0, [2, 3, 4]]],
+    6: [[0, 1, [1, 3, 5]], [-1, 0, [2, 3, 4]]]
+  };
+
+  return explorePath(0, 0);
+
+  function isValid(x, y) {
+    return x >= 0 && x < rows && y >= 0 && y < cols;
+  }
+
+  function explorePath(x, y, visited = new Set()) {
+    if (!isValid(x, y) || visited.has(`${x},${y}`)) return false;
+    if (x === rows - 1 && y === cols - 1) return true;
+
+    visited.add(`${x},${y}`);
+    const street = grid[x][y];
+
+    for (const [dx, dy, validStreets] of directions[street]) {
+      const newX = x + dx;
+      const newY = y + dy;
+      if (isValid(newX, newY) && validStreets.includes(grid[newX][newY])) {
+        if (explorePath(newX, newY, visited)) return true;
+      }
+    }
+
+    return false;
+  }
+};