题解 | #高精度整数加法#

import java.util.Scanner;

// 注意类名必须为 Main, 不要有任何 package xxx 信息
public class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        // 注意 hasNext 和 hasNextLine 的区别
        while (in.hasNextLine()) {
            String s1 = in.nextLine();
            String s2 = in.nextLine();
            int delta = s1.length() - s2.length();
            StringBuffer sb1 = new StringBuffer(s1).reverse();
            StringBuffer sb2 = new StringBuffer(s2).reverse();
            if (delta < 0) {
                for (int i = 0 ; i < Math.abs(delta) ; ++i) {
                    sb1.append('0');
                }
            } else if (delta > 0) {
                for (int i = 0 ; i < delta ; ++i) {
                    sb2.append('0');
                }
            }

            sb1 = sb1.reverse();
            sb2 = sb2.reverse();
            //System.out.println(sb1);
            //System.out.println(sb2);

            int jinwei = 0;
            //StringBuilder sb = new StringBuilder();
            for (int i = sb1.length()-1 ; i >=0 ; --i) {
                int a = Integer.valueOf(sb1.charAt(i) + "");
                int b = Integer.valueOf(sb2.charAt(i) + "");
                if (a + b + jinwei >= 10) {
                    sb1.setCharAt(i, (char)(a + b - 10 + '0' + jinwei));
                    jinwei = 1;
                } else {
                    sb1.setCharAt(i, (char)(a + b + '0' + jinwei));
                    jinwei = 0;
                }
            }
            if (jinwei == 1) {
                sb1 = sb1.reverse().append('1').reverse();
            }
            System.out.println(sb1.toString());


        }
    }
}