// @Title: 字符串相加 (Add Strings)
// @Author: qisiii
// @Date: 2024-05-10 16:04:46
// @Runtime: 1 ms
// @Memory: 41.7 MB
// @comment: 
// @flag: 
class Solution {
    public String addStrings(String s, String t) {
        if(s.length()==0||t.length()==0){
            return s+t;
        }
        int max=Math.max(s.length(),t.length());
        char[] result= new char[max+1];
        int sl=s.length()-1;
        int tl=t.length()-1;
        int jin=0;
        while(sl>=0||tl>=0){
            int svalue=sl>=0?s.charAt(sl)-'0':0;
            int tvalue=tl>=0?t.charAt(tl)-'0':0;
            int cur=(svalue+tvalue+jin)%10;
            jin=(svalue+tvalue+jin)/10;
            result[max]=(char) (cur+'0');
            sl--;tl--;max--;
        }
        result[max]=(char)(jin+'0');
        return handleZero(result);
    }

    public String handleZero(char[] result){
        int firstN0=0;
        while(firstN0<result.length&&result[firstN0]=='0'){
            firstN0++;
        }
        if(firstN0==result.length){
            return "0";
        }
        return new String(result).substring(firstN0);
    }
}