feat: add js solution to 127 word ladder

Author: abstrekt

javascript/127-Word-Ladder.js

@@ -0,0 +1,34 @@
+var ladderLength = function (beginWord, endWord, wordList) {
+  if (!wordList.includes(endWord)) return 0;
+  let patternMap = {};
+  wordList.push(beginWord);
+
+  for (let word of wordList) {
+    for (let x = 0; x < word.length; x++) {
+      const pattern = word.slice(0, x) + "*" + word.slice(x + 1);
+      patternMap[pattern] = patternMap[pattern] || [];
+      patternMap[pattern].push(word);
+    }
+  }
+
+  let wordCount = 1,
+    queue = [beginWord],
+    visited = [beginWord];
+  while (queue.length) {
+    const levelSize = queue.length;
+    for (let x = 0; x < levelSize; x++) {
+      const word = queue.shift();
+      if (word === endWord) return wordCount;
+      for (let x = 0; x < word.length; x++) {
+        const pattern = word.slice(0, x) + "*" + word.slice(x + 1);
+        for (let nei of patternMap[pattern]) {
+          if (nei in visited) continue;
+          visited[nei] = true;
+          queue.push(nei);
+        }
+      }
+    }
+    wordCount += 1;
+  }
+  return 0;
+};