Leetcode专题-415-字符串相加

leetcode链接：
https://leetcode.cn/problems/add-strings/description/
解题思路：

func addStrings(num1 string, num2 string) string {
    nb1, nb2 := []byte(num1), []byte(num2)
    if len(nb1) < len(nb2) {
        nb1, nb2 = nb2, nb1
    }

    sum := byte(0)
    for i, j := len(nb1)-1, len(nb2)-1; i >= 0; i, sum = i-1, sum/10 {
        if j >= 0 {
            sum += nb2[j] - '0'
            j--
        }
        sum += nb1[i] - '0'
        nb1[i] = (sum % 10) + '0'
    }
    if sum != 0 {
        nb1 = append([]byte{'1'}, nb1...)
    }
    return string(nb1)
}