力扣题解

截屏2020-08-21 下午3.02.05.png

var myAtoi = function(str) {
    let string = str.replace(/^\s*/,'');
    if(/^[-]?\d/.test(string) || /^[+]?\d/.test(string) ){
        let num = string.match(/(^[-]?[+]?\d*)/)[1];
        if( Number(num) > Math.pow(-2,31) &&  Number(num) < Math.pow(2,31)-1) {
            return Number(num);
        }else {
            if(num[0] == '-') {
                return Math.pow(-2,31)
            } else {
                return Math.pow(2,31)-1
            }
        }
    }else {
        return 0;
    }
};

截屏2020-08-21 下午3.04.10.png

var countSubstrings = function(s) {
    if(s.length>1000) {
        alert('长度不超过 1000') 
    }else{
        let number = 0;
        for(let i = 0; i < s.length; i++){
            for(let j=i+2; j<s.length+1; j++) {
                let str = s.slice(i, j)
                let start = 0;
                let end = str.length-1;
                while(str[start] == str[end]) {
                    start++;
                    end--;
                    if(start >= end) {
                        number++;
                        break
                    }
                }
            }
        }
        return number+ s.length;
    }
};

截屏2020-08-31 下午5.14.34.png

/**
 * @param {number[][]} rooms
 * @return {boolean}
 */
var canVisitAllRooms = function(rooms) {
    let n = 0 ;
    let key = [0];
    while (key.length > n) {
        key = key.concat([...new Set(rooms[key[n]].filter(item=> !key.includes(item)))]);
        n++;
    }
    if(key.length == rooms.length) {
        return true
    }else{
        return false
    }
};