题解 | #高精度整数加法#

import java.util.*;
public class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        while (in.hasNext()) { 
            String a = in.next();
            String b = in.next();
            boolean f = a.length()>=b.length();
            boolean flag = false;
            char[] cBig = f?a.toCharArray():b.toCharArray();
            char[] cSmall = f?b.toCharArray():a.toCharArray();
            //相加后的字符数组
            char[] newC = new char[cBig.length+1];
            Arrays.fill(newC,'0');
            int t = 0;
            //以短字符串为基准，分别将两字符串从后面的每一个字符相加
            for(int i = cSmall.length-1; i>=0; i--){
                if(flag){
                    t = cBig[i+cBig.length-cSmall.length] + cSmall[i] + 1 - 48 - 48;
                }else{
                    t = cBig[i+cBig.length-cSmall.length] + cSmall[i] - 48 - 48;
                }
                flag = false;
                //相加大于10，进位
                if(t>=10){
                    flag = true;
                    t -= 10;
                }
                newC[i+cBig.length-cSmall.length+1] = (char)(t + 48);
            }
            //短字符串相加完成后，将长字符串剩余字符给newC
            int j = newC.length-cSmall.length-1;
            for(; j>=newC.length-cBig.length; j--){
                if(flag){
                    t = (char)(cBig[j-1] + 1 - 48);
                    flag = false;
                    if(t>=10){
                        flag = true;
                        t -= 10;
                    }
                    newC[j] = (char)(t + 48);
                }else{
                    newC[j] = cBig[j-1]; 
                }
            }
            if(flag){
                newC[0] = (char)1+48;
                System.out.print(String.copyValueOf(newC));
            }else{
                System.out.print(String.copyValueOf(newC).substring(1,newC.length));
            }
            
        }
    }
}