字符串解码(⭐⭐)

题目

https://leetcode-cn.com/problems/decode-string/

解题

/**
 * @param {string} s
 * @return {string}
 */
var decodeString = function(s) {
    let multi  = 0 
    let res = ''
    const stack = []
    for (let c of s) {
        if (c === '[') {
            stack.push([multi, res])
            res = '', multi = 0
        } else if (c === ']') {
            const pop = stack.pop()
            const cur_mult = pop[0]
            const last_res = pop[1]
            //    之前结果       // 
            res = last_res + new Array(cur_mult).fill(res).join('')
        } else if (c >= '0' && c <= '9') {
            multi = multi * 10 + Number(c)
        } else {
            // 记录重复单元
            res += c
        }
    }
    return res
};