日常刷题0x28之未出新手村

如果不小心网友来到了这里请网友自动飘走，浪费你们时间表示歉意。该系列博客的目的是：想作为自律工具和朋友一起每天刷几道题作为打卡督促的功能，没有什么可参考学习的东西，也不是刷博客量充大佬的目的

题号：208

/**
 * Initialize your data structure here.
 */
var Trie = function () {
    //根节点
    this.root = {}
};

/**
 * Inserts a word into the trie. 
 * @param {string} word
 * @return {void}
 */
Trie.prototype.insert = function (word) {
    let curNode = this.root
    for (let i = 0; i < word.length; i++) {
        let letter = word[i]
        if (!curNode[letter]) {
            curNode[letter] = {}
        }
        curNode = curNode[letter]
    }
    curNode.isEnd = true
};

/**
 * Returns if the word is in the trie. 
 * @param {string} word
 * @return {boolean}
 */
Trie.prototype.search = function (word) {
    let curNode = this.root
    for (let i = 0; i < word.length; i++) {
        let letter = word[i]
        if (curNode[letter]) {
            curNode = curNode[letter]
        } else {
            return false
        }
    }
    return curNode.isEnd ? true : false
};

/**
 * Returns if there is any word in the trie that starts with the given prefix. 
 * @param {string} prefix
 * @return {boolean}
 */
Trie.prototype.startsWith = function (prefix) {
    let curNode = this.root
    for (let i = 0; i < prefix.length; i++) {
        let letter = prefix[i]
        if (curNode[letter]) {
            curNode = curNode[letter]
        } else {
            return false
        }
    }
    return true
};

题号：3

var lengthOfLongestSubstring = function (s) {
    //滑动窗口，map记录是否重复
    let map = new Map()
    let left = 0, right = 0, max = 0
    while (right < s.length) {
        let letter = s[right]
        if (map.has(letter)) {
            let count = map.get(letter)
            count++
            map.set(letter, count)
        } else {
            max = Math.max(max, right - left + 1)
            map.set(letter, 1)
        }

        if (map.get(letter) > 1) {
            //收缩尾部使窗口字母满足题意
            while (true) {
                //收缩的过程中遇到count为1的从map中删除然后
                //left + 1，遇到count为2的时候说明找到重复元素
                //跳过该元素使count - 1
                let count = map.get(s[left])
                if (count == 2) {
                    count--
                    map.set(s[left], count)
                    left++
                    break
                }
                map.delete(s[left])
                left++
            }
        }
        right++
    }
    return max
};

题号：206

//递归反转
var reverseList = function (head) {

    let helper = (node) => {
        if (node == null) {
            return null
        }
        let preNode = helper(node.next)
        if (preNode == null) {
            head = node
        } else {
            preNode.next = node
        }
        node.next = null
        return node
    }
    helper(head)
    return head
};

题号：15

var threeSum = function (nums) {
    //升序排序
    nums.sort((a, b) => {
        return a - b
    })
    let result = []
    for (let i = 0; i < nums.length; i++) {
        //这里对a进行去重
        if (i != 0 && nums[i] == nums[i - 1]) {
            continue
        }
        const a = nums[i]
        let left = i + 1, right = nums.length - 1
        while (left < right) {
            if (a + nums[left] + nums[right] > 0) {
                right--
            } else if (a + nums[left] + nums[right] < 0) {
                left++
            } else {
                result.push([a, nums[left], nums[right]])
                //这里对b进行去重
                while (left < right) {
                    if (nums[left] == nums[left + 1]) {
                        left++
                    } else {
                        left++
                        break
                    }
                }
                //这里对c进行去重
                while (right > left) {
                    if (nums[right] == nums[right - 1]) {
                        right--
                    } else {
                        right--
                        break
                    }
                }
            }
        }
    }
    return result
};