1301~1350

/**
* @param a: a string
* @param b: a string
* @return: return the sum of two strings
*/
import (
    "strconv"
)
func SumofTwoStrings(a string, b string) string {
    // write your code here
    res := ""
    indexA, indexB := len(a)-1, len(b)-1
    for indexA >= 0 && indexB >= 0 {
        temp := a[indexA] - '0' + b[indexB] - '0'
        res = strconv.Itoa(int(temp)) + res
        indexA--
        indexB--
    }
    if indexA >= 0 {
        res = a[0:indexA+1] + res
    }
    if indexB >= 0 {
        res = b[0:indexB+1] + res
    }
    return res
}