leetcode-将整数转换为罗马数字重要思想：把数字拆分成千位，百位，十位和各位的数，然后依次用+号将字符串连接起来！

/**
 * @param {number} num
 * @return {string}
 */
 //2999
//重要思想：把数字拆分成千位，百位，十位和各位的数
var intToRoman = function(num) {
    let  thousands = new Array("", "M", "MM", "MMM")
    let handreds = new Array("", "C", "CC", "CCC", "CD", "D","DC","DCC","DCCC","CM")
    let tens = new Array("", "X","XX","XXX","XL","L","LX","LXX","LXXX","XC")
    let ones = new Array("", "I", "II","III","IV","V","VI","VII","VIII","IX")
    let res = thousands[Math.floor(num / 1000)] + handreds[Math.floor(num % 1000 / 100)] + tens[Math.floor(num % 100 / 10)] + ones[Math.floor(num % 10)]
    return res

};