剑指 Offer II 108. 单词演变

感觉结果是对的。。 但是超时了= =。。

func ladderLength(_ beginWord: String, _ endWord: String, _ wordList: [String]) -> Int {

        if !wordList.contains(endWord) {
            return 0
        }
        var wordSet :Set<String> = Set.init(wordList)
        var tempArray = [String]()
        tempArray.append(beginWord)
        var count = 1
        while tempArray.count > 0 {
            
            let len = tempArray.count
            
            for _ in 0..<len{
                
                let cur = tempArray.removeLast()
                if cur == endWord {
                    return count
                }
                for w in wordSet {
                    if canChange(w, cur) {
                        wordSet.remove(w)
                        tempArray.insert(w, at: 0)
                    }
                }
                
            }
        
            count += 1

        }
   
        return 0
    
    
    }

    func canChange(_ v1:String, _ v2:String) -> Bool {
        let array1 = Array(v1)
        let array2 = Array(v2)
        let len = array1.count
        var count = 0
        for i in 0..<len {
            
            if array1[i] != array2[i] {
                count += 1
            }
            if count > 1 {
                return false
            }
            
        }
        return true
    }

换种写法 a的ascil码 97 可能这样写加快了转换速度= =。。

 func ladderLength(_ beginWord: String, _ endWord: String, _ wordList: [String]) -> Int {

        if !wordList.contains(endWord) {
            return 0
        }
        var wordSet :Set<String> = Set.init(wordList)
        var tempArray = [String]()
        tempArray.append(beginWord)
        var count = 1
        while tempArray.count > 0 {
            
            let len = tempArray.count
            
            for _ in 0..<len{
                
                let cur = tempArray.removeLast()
                if cur == endWord {
                    return count
                }
                for w in getNext(cur) {
                    if wordSet.contains(w){
                        wordSet.remove(w)
                        tempArray.insert(w, at: 0)
                    }
                }
                
            }
        
            count += 1

        }
  
        return 0
    
    
    }
  
    
    
    func getNext(_ word:String) -> [String] {
        var arr = Array(word)
        var res = [String]()
        let len = arr.count

        for i in 0..<len {
            let temp = arr[i]
            for j in 0..<26 {
                arr[i] = Character(UnicodeScalar(97 + j)!)
                if temp != arr[i] {
                    res.append(String(arr))
                }
            }
            //还原回去
            arr[i] = temp
        }
        
        return res
        
    }