用 javascript 分类刷 leetcode22. 字典树 (图文视频讲解)

var Trie = function() {    this.children = {};};
Trie.prototype.insert = function(word) {    let nodes = this.children;    for (const ch of word) {//循环word        if (!nodes[ch]) {//当前字符不在子节点中 则创建一个子节点到children的响应位置            nodes[ch] = {};        }        nodes = nodes[ch];//移动指针到下一个字符子节点    }    nodes.isEnd = true;//字符是否结束};
Trie.prototype.searchPrefix = function(prefix) {    let nodes = this.children;    for (const ch of prefix) {//循环前缀        if (!nodes[ch]) {//当前字符不在子节点中 直接返回false            return false;        }        nodes = nodes[ch];//移动指针到下一个字符子节点    }    return nodes;//返回最后的节点}
Trie.prototype.search = function(word) {    const nodes = this.searchPrefix(word);      //判断searchPrefix返回的节点是不是字符串的结尾的字符    return nodes !== undefined && nodes.isEnd !== undefined;};
Trie.prototype.startsWith = function(prefix) {    return this.searchPrefix(prefix);};

var findWords = function (board, words) {    const trie = new Trie();    const dxys = [        [0, -1],        [-1, 0],        [0, 1],        [1, 0],    ];    const xLen = board.length,        yLen = board[0].length;    const visited = {};    const ret = [];
    // 构建Trie    for (let word of words) {        trie.insert(word);    }
    // DFS board    const dfs = (x, y, nodes, str) => {        if (nodes[board[x][y]].isEnd) {            ret.push(str + board[x][y]);            // 置为false是为了防止重复将字符串加入到ret中            nodes[board[x][y]].isEnd = false;        }
        // 处理本层状态        nodes = nodes[board[x][y]];        str += board[x][y];
        // 向四联通方向检索        visited[x * 100 + y] = true;        for (let [dx, dy] of dxys) {            const newX = x + dx,                newY = y + dy;
            if (                newX < 0 ||                newY < 0 ||                newX >= xLen ||                newY >= yLen ||                !nodes[board[newX][newY]] ||                visited[newX * 100 + newY]            )                continue;
            dfs(newX, newY, nodes, str);        }        visited[x * 100 + y] = false;    };
    for (let x = 0; x < xLen; x++) {        for (let y = 0; y < yLen; y++) {            if (trie.children[board[x][y]]) dfs(x, y, trie.children, "");        }    }
    return ret;};
var Trie = function () {    this.children = {};};
Trie.prototype.insert = function (word) {    let nodes = this.children;    for (const ch of word) {//循环word        if (!nodes[ch]) {//当前字符不在子节点中 则创建一个子节点到children的响应位置            nodes[ch] = {};        }        nodes = nodes[ch];//移动指针到下一个字符    }    nodes.isEnd = true;//字符是否结束};

var longestWord = function (words) {    let set = new Set()    words.forEach(v => set.add(v))//set方便查找        //先按长度排序，在按字典序    words.sort((a, b) => a.length === b.length ? a.localeCompare(b) : b.length - a.length)    for (let i = 0; i < words.length; i++) {        let flag = true        for (let j = 1; j < words[i].length; j++) {            if (!set.has(words[i].substring(0, j))) {//查看set中是否有该字符串的每个子串                flag = false                break            }        }        if (flag) {            return words[i]        }    }    return ''};

var longestWord = function (words) {    const trie = new Trie()    words.forEach(word => {//将所有字符串插入trie中        trie.insert(word)    })    let res = ''    const _helper = (nodes, path) => {        if (path.length > res.length || (res.length === path.length && res > path)) {            res = path        }                //{a:{b1:{c1:{isEnd: true}},b2:{c2:{isEnd: true}}}}        for (const [key, value] of Object.entries(nodes)) {                    if (value.isEnd) {//如果当前字符是某一个字符串的结尾                path += key                _helper(value, path)//递归寻找                path = path.slice(0, -1)//回溯            }        }    }    _helper(trie.children, '')//递归寻找那个长度最大的单词    return res}
var Trie = function() {    this.children = {};};
Trie.prototype.insert = function(word) {    let nodes = this.children;    for (const ch of word) {//循环word        if (!nodes[ch]) {//当前字符不在子节点中 则创建一个子节点到children的响应位置            nodes[ch] = {};        }        nodes = nodes[ch];//移动指针到下一个字符    }    nodes.isEnd = true;//字符是否结束};