题解 | #大数加法#

import java.util.*;


public class Solution {
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     * 计算两个数之和
     * @param s string字符串 表示第一个整数
     * @param t string字符串 表示第二个整数
     * @return string字符串
     */
    public String solve (String s, String t) {
        StringBuilder s1, t1;
        if (s.length() >= t.length()) {
            s1 = new StringBuilder(s).reverse();
            t1 = new StringBuilder(t).reverse();
        } else {
            s1 = new StringBuilder(t).reverse();
            t1 = new StringBuilder(s).reverse();
        }

        int i = 0, j = 0;
        int slen = s1.length();
        int tlen = t1.length();

        while(i < slen && j < tlen) {
            int ds = s1.charAt(i)-'0';
            int dt = t1.charAt(j)-'0';
            s1.setCharAt(i, (char) (ds + dt + '0'));
            i++;
            j++;
        }
        i = 0;
        int x = 0;
        int r = 0;
        while(i < slen) {
            int d = s1.charAt(i) - '0' + x;
            r = d % 10;
            x = d / 10;
            s1.setCharAt(i, (char)(r + '0'));
            i++;
        }
        if (x != 0) {
            s1.append((char)(x+'0'));
        }
        return s1.reverse().toString();
    }
}