Brace Expansion

Description

null

Solution(javascript)

/**
 * @param {string} S
 * @return {string[]}
 */
var expand = function(S) {
    const arr = []
    let tempArr = []
    let tempStr = ""
    let start = false
    for(let c of S) {
        if(c === "{") {
            start = true
            if(tempStr.length > 0) {
                arr.push([tempStr])
                tempStr = ""
            }
        } else if(c === "}") {
            start = false
            if(tempArr.length > 0) {
                arr.push(tempArr)
                tempArr = []    
            }
            
        }else if(c===",") {
            continue
        } else {
            if(start) {
                tempArr.push(c)
            } else {
                tempStr += c   
            }
        }
    }
    if(tempStr.length > 0) {
         arr.push([tempStr])
    }
    let result = []
    const aux = (index=0, current = "") => {
        if(index >= arr.length) {
            result.push(current)
            return
        }
        arr[index].forEach(s => aux(index+1, current + s))
    }
    aux()
    return result.sort()
};