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
        String a = in.nextLine();
        String b = in.nextLine();
        StringBuilder sb = new StringBuilder();
        int max = Math.max(a.length(), b.length());
        if(a.length() < b.length()) {
            int x = b.length() - a.length();
            for(int i = 0; i < x; i++) {
                a = "0" + a;
            }
        } else {
            int x = a.length() - b.length();
            for(int i = 0; i < x; i++) {
                b = "0" + b;
            }
        }
        // 是否进位
        boolean flag = false;
        for(int i = max - 1; i >=0; i--) {
            int m = Integer.valueOf(String.valueOf(a.charAt(i)));
            int n = Integer.valueOf(String.valueOf(b.charAt(i)));
            int result = m + n + (flag?1:0);
            sb.append(result%10);
            flag = result / 10 > 0;
        }
        if(flag) {
            sb.append("1");
        }
        sb.reverse();
        System.out.println(sb.toString());
    }
}