Create 126-word-ladder-ii.js

Author: everthis

126-word-ladder-ii.js

@@ -0,0 +1,64 @@
+/**
+ * @param {string} beginWord
+ * @param {string} endWord
+ * @param {string[]} wordList
+ * @return {string[][]}
+ */
+const findLadders = function (beginWord, endWord, wordList) {
+  const res = []
+  if (!wordList.includes(endWord)) return res
+  const set1 = new Set([beginWord]),
+    set2 = new Set([endWord]),
+    wordSet = new Set(wordList),
+    temp = [beginWord]
+  const map = new Map()
+  const traverse = (set1, set2, dir) => {
+    if (set1.size === 0) return false
+    if (set1.size > set2.size) return traverse(set2, set1, !dir)
+    for (const val of set1.values()) {
+      if (wordSet.has(val)) wordSet.delete(val)
+    }
+    for (const val of set2.values()) {
+      if (wordSet.has(val)) wordSet.delete(val)
+    }
+    const set = new Set()
+    let done = false
+    for (const str of set1.values()) {
+      for (let i = 0; i < str.length; i++) {
+        for (let ch = 'a'.charCodeAt(); ch <= 'z'.charCodeAt(); ch++) {
+          const word =
+            str.slice(0, i) + String.fromCharCode(ch) + str.slice(i + 1)
+          const key = dir ? str : word
+          const val = dir ? word : str
+          const list = map.get(key) || []
+          if (set2.has(word)) {
+            done = true
+            list.push(val)
+            map.set(key, list)
+          }
+          if (!done && wordSet.has(word)) {
+            set.add(word)
+            list.push(val)
+            map.set(key, list)
+          }
+        }
+      }
+    }
+    return done || traverse(set2, set, !dir)
+  }
+  const dfs = (word) => {
+    if (word === endWord) {
+      res.push(temp.slice())
+      return
+    }
+    const nei = map.get(word) || []
+    for (const w of nei) {
+      temp.push(w)
+      dfs(w)
+      temp.pop()
+    }
+  }
+  traverse(set1, set2, true)
+  dfs(beginWord)
+  return res
+}