题解 | #高精度整数加法#

import java.util.Scanner;
public class Main {
public static void main(String[] args){
Scanner s = new Scanner(System.in);
while(s.hasNext()){
//String s1 = "";//s.nextLine();
//String s2 = "";//s.nextLine();9876543210
//630222
//6450
//623192091
//14426202982932

        String s1 = s.nextLine();
        String s2 = s.nextLine();
        s1 = s1.replace(" ","");
        s2 = s2.replace(" ","");
        //1234567890
        //s1="623192091";s2="14426202982932";
        //s1="630222";s2="6450";
        s1=reverse(s1);
        s2=reverse(s2);
        if(s1.length()>s2.length()){
            System.out.println(fun(s1,s2));
        }else if(s1.length()<s2.length()){
            System.out.println(fun(s2,s1));
        }else {
            System.out.println(fundeng(s2,s1));
        }
    }
}
public static String reverse(String s1){
    String s = "";
    for(int i = s1.length()-1;i>=0;i--){
        s=s+s1.charAt(i);
    }
    //s = s.replace(" ","");
    return s;
}
public static String fun(String s1,String s2){//s1比s2长,放进来的是翻转过的，0位是尾
    int len1 = s1.length();
    int len2 = s2.length();//取得长度
    int num,count=0;
    String ss = "";//中间用的字符串
    String swei = s1.substring(0,len2+1);//和s2长度一样的先切出来
    String stou = s1.substring(len2,len1);//剩下的就是头
    for(int i = 0;i<len2;i++){//先把长度相同的算一下
        num = swei.charAt(i)-'0'+s2.charAt(i)-'0'+count;//看看有无进位
        if(num>9){//看看是否需要进位
            num = num%10;//取个位
            count=1;//进位加一
        }else{
            count = 0;
        }
        ss = ss + num;//把算出来的各位连起来，顺序是反的
    }
    if(count==1){//有进位的话需要计算后面的部分
        for(int i = 0;i < len1-len2;i++){//
            num = stou.charAt(i)-'0'+count;
            if(num>9){//看看是否需要进位
                num = num%10;//取个位
                count=1;//进位加一
            }else{
                count = 0;
            }
            ss = ss + num;//把算出来的各位连起来，顺序是反的
        }
        }else{
        ss = ss + stou;
    }
    return reverse(ss);
}
public static String fundeng(String s1,String s2){//s1比s2长,放进来的是翻转过的，0位是尾
    int len1 = s1.length();
    int len2 = s2.length();//取得长度
    int num,count=0;
    String ss = "";//中间用的字符串
    //String swei = s1.substring(1,len2+1);//和s2长度一样的先切出来
    //String stou = s1.substring(len2+1,len1);//剩下的就是头
    for(int i = 0;i<len2;i++){//先把长度相同的算一下
        num = s1.charAt(i)-'0'+s2.charAt(i)-'0'+count;//看看有无进位
        if(num>9){//看看是否需要进位
            num = num%10;//取个位
            count=1;//进位加一
        }else{
            count = 0;
        }
        ss = ss + num;//把算出来的各位连起来，顺序是反的
    }
    if(count==1){
        ss = ss + 1;
    }

    return reverse(ss);
}

}