题解 | #大数加法#

按正常加法思维，简单易懂。

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) {
        // write code here
        if(s.length()==0) {return t;}
        if(t.length()==0) {return s;}
        String sum = "";
        String[] strArray = getComparedStr(s,t);
        return computStr(strArray);
    }

    public String computStr(String[] strArray){
        String longStr = strArray[0];
        String shortStr = strArray[1];
    
        int n = 0;
        StringBuilder now = new StringBuilder();
        int[] sum;
        for(int i = longStr.length()-1, j = shortStr.length()-1;i>=0; i--, j--)
        {
            char shortChar = j>=0?shortStr.charAt(j):'0';
            sum = sumOneChar(shortChar, longStr.charAt(i), n);
            n = sum[0];
            now.insert(0, sum[1]);
        }
        if(n != 0)
        {
            now.insert(0, n);
        }
        return now.toString();
    }

    public int[] sumOneChar(char a, char b, int n)
    {
        int[] sum = {0, 0};
        int res =  (a - '0') + (b - '0') + n;
        sum[1] = res%10;
        sum[0] = res/10;
        return sum;
    }

    public String[] getComparedStr(String s, String t)
    {
        String res[] = {"",""};
        if(s.length()>t.length()){
            res[0] = s;
            res[1] = t;
        }
        else{
            res[0] = t;
            res[1] = s;
        }
        return res;
    }
}