leetcode Day66 剑指 9-10

1161. 最大层内元素和

var maxLevelSum = function(root) {
    if(!root){
        return 0
    }
    let res=[]
    let queue=[root]
    while(queue.length){
        let cur=0
        let l=queue.length
        for(let i=0;i<l;i++){
            let node=queue.shift()
            cur+=node.val
            if(node.left){
                queue.push(node.left)
            }
            if(node.right){
                queue.push(node.right)
            }
        }
        res.push(cur)
    }
    return res.indexOf(Math.max(...res))+1
};

剑指 Offer 09. 用两个栈实现队列

var CQueue = function() {
    this.inStack=[]
    this.outStack=[]
};

/** 
 * @param {number} value
 * @return {void}
 */
CQueue.prototype.appendTail = function(value) {
    this.inStack.push(value)
};

/**
 * @return {number}
 */
CQueue.prototype.deleteHead = function() {
    if(!this.outStack.length){
        if(!this.inStack.length){
            return -1
        }
        while(this.inStack.length){
            this.outStack.push(this.inStack.pop())
        }
    }
    return this.outStack.pop()
};

剑指 Offer 10- I. 斐波那契数列

var fib = function(n) {
    let dp=new Array(n).fill(0)
    dp[0]=0
    dp[1]=1
    for(let i=2;i<n+1;i++){
        dp[i]=(dp[i-1]+dp[i-2])%(1000000007)
    }
    return dp[n]
};

剑指 Offer 10- II. 青蛙跳台阶问题

var numWays = function(n) {
    let dp=new Array(n).fill(0)
    dp[0]=1
    dp[1]=1
    dp[2]=2
    for(let i=3;i<n+1;i++){
        dp[i]=(dp[i-1]+dp[i-2])%1000000007
    }
    return dp[n]
};