题解 | #高精度整数加法#

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

public class Main {
    public static void main(String[] args) {
        BufferedReader r = new BufferedReader(new InputStreamReader(System.in));
        String a, b, and2 = "";
        try {
            a = r.readLine();
            b = r.readLine();
        } catch (IOException e) {
            throw new RuntimeException(e);
        }
        char[] chs1 = a.toCharArray();
        char[] chs2 = b.toCharArray();
        int[] arr1 = new int[10001];
        int[] arr2 = new int[10001];
        int[] arr3 = new int[10001];
        int i, j = 0, k = 0, l = chs1.length, t;
        boolean lift = false;
        for (i = l - 1; i > -1; i--) {//字符串反向，便于计算
            arr1[j++] = chs1[i] - '0';
        }
        l = chs2.length;
        for (i = l - 1; i > -1; i--) {//字符串反向，便于计算
            arr2[k++] = chs2[i] - '0';
        }
        i = 0;
        while (i < 10001) {
            t = arr1[i] + arr2[i];//计算该位之和
            if (lift) t++;//如果前一位有进1，则t自加
            if (t > 9) {//如果进1
                lift = true;
                t -= 10;
            } else lift = false;
            arr3[i] = t;
            i++;
        }
        i = Math.max(j, k);
        if (arr3[i] == 0) i--;
        while (i > -1) {
            and2 = and2 + arr3[i];
            i--;
        }
        System.out.print(and2);
    }
}