Add solution #773

Author: JoshCrozier

README.md

@@ -585,6 +585,7 @@
 768|[Max Chunks To Make Sorted II](./0768-max-chunks-to-make-sorted-ii.js)|Hard|
 769|[Max Chunks To Make Sorted](./0769-max-chunks-to-make-sorted.js)|Medium|
 770|[Basic Calculator IV](./0770-basic-calculator-iv.js)|Hard|
+773|[Sliding Puzzle](./0773-sliding-puzzle.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/0773-sliding-puzzle.js

@@ -0,0 +1,51 @@
+/**
+ * 773. Sliding Puzzle
+ * https://leetcode.com/problems/sliding-puzzle/
+ * Difficulty: Hard
+ *
+ * On an 2 x 3 board, there are five tiles labeled from 1 to 5, and an empty square represented by
+ * 0. A move consists of choosing 0 and a 4-directionally adjacent number and swapping it.
+ *
+ * The state of the board is solved if and only if the board is [[1,2,3],[4,5,0]].
+ *
+ * Given the puzzle board board, return the least number of moves required so that the state of the
+ * board is solved. If it is impossible for the state of the board to be solved, return -1.
+ */
+
+/**
+ * @param {number[][]} board
+ * @return {number}
+ */
+var slidingPuzzle = function(board) {
+  const target = '123450';
+  const moves = [
+    [1, 3], [0, 2, 4], [1, 5],
+    [0, 4], [1, 3, 5], [2, 4]
+  ];
+
+  const start = board.flat().join('');
+  if (start === target) return 0;
+
+  const queue = [[start, 0]];
+  const seen = new Set([start]);
+
+  while (queue.length) {
+    const [state, steps] = queue.shift();
+    const index = state.indexOf('0');
+
+    for (const next of moves[index]) {
+      const chars = state.split('');
+      [chars[index], chars[next]] = [chars[next], chars[index]];
+      const nextState = chars.join('');
+
+      if (nextState === target) return steps + 1;
+
+      if (!seen.has(nextState)) {
+        seen.add(nextState);
+        queue.push([nextState, steps + 1]);
+      }
+    }
+  }
+
+  return -1;
+};