415.字符串相加

题解

class Solution {
    public String addStrings(String num1, String num2) {
            int i =num1.length()-1, j = num2.length()-1, add = 0;
            StringBuffer ans = new StringBuffer();
            while(i >= 0 || j >= 0 || add != 0){
                int x = i >= 0 ? num1.charAt(i)-'0' : 0;
                int y = j >= 0 ? num2.charAt(j)-'0' : 0;
                int result = x+y+add;
                ans.append(result%10);
                add = result/10;
                i--;
                j--;
            }
            return ans.reverse().toString();
    }
}