Create 127-word-ladder.js

Author: everthis

127-word-ladder.js

@@ -0,0 +1,32 @@
+/**
+ * @param {string} beginWord
+ * @param {string} endWord
+ * @param {string[]} wordList
+ * @return {number}
+ */
+const ladderLength = function(beginWord, endWord, wordList) {
+  const list = new Set(wordList)
+  if (!list.has(endWord)) return 0
+  let one = new Set([beginWord])
+  let two = new Set([endWord])
+  let step = 1
+  while (one.size && two.size) {
+    let temp = new Set()
+    if (two.size < one.size) [one, two] = [two, one]
+    for (const word of one) {
+      for (let i = 0; i < word.length; i++) {
+        for (let j = 0; j < 26; j++) {
+          const candidate =
+            word.slice(0, i) + String.fromCharCode(97 + j) + word.slice(i + 1)
+          if (two.has(candidate)) return step + 1
+          if (!list.has(candidate)) continue
+          temp.add(candidate)
+          list.delete(candidate)
+        }
+      }
+    }
+    ;[one, temp] = [temp, one]
+    step++
+  }
+  return 0
+}