题解 | #整数加法#

#include <iostream>
#include <string>
using namespace std;

// 判断字符串是否合法（只包含数字）
bool isLegal(const string& s) {
    for (char c : s) {
        if (c < '0' || c > '9') return false;
    }
    return true;
}

int main() {
    string a, b;
    while (cin >> a >> b) {
        // 判断输入是否合法
        if (!isLegal(a) || !isLegal(b)) {
            cout << "error" << endl;
            continue;
        }
        
        // 将字符串转为数字数组，反向存储
        int len = max(a.length(), b.length()) + 1;
        vector<int> result(len, 0);
        
        // 从低位开始相加
        for (int i = 0; i < a.length(); i++) {
            result[i] += a[a.length()-1-i] - '0';
        }
        for (int i = 0; i < b.length(); i++) {
            result[i] += b[b.length()-1-i] - '0';
        }
        
        // 处理进位
        for (int i = 0; i < len-1; i++) {
            result[i+1] += result[i] / 10;
            result[i] %= 10;
        }
        
        // 去除前导零并输出
        int start = len-1;
        while (start > 0 && result[start] == 0) start--;
        for (int i = start; i >= 0; i--) {
            cout << result[i];
        }
        cout << endl;
    }
    return 0;
}

import java.util.Scanner;

public class Main {
    // 判断字符串是否合法（只包含数字）
    public static boolean isLegal(String s) {
        for (char c : s.toCharArray()) {
            if (c < '0' || c > '9') return false;
        }
        return true;
    }
    
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        while (sc.hasNext()) {
            String a = sc.next();
            String b = sc.next();
            
            // 判断输入是否合法
            if (!isLegal(a) || !isLegal(b)) {
                System.out.println("error");
                continue;
            }
            
            // 将字符串转为数字数组，反向存储
            int len = Math.max(a.length(), b.length()) + 1;
            int[] result = new int[len];
            
            // 从低位开始相加
            for (int i = 0; i < a.length(); i++) {
                result[i] += a.charAt(a.length()-1-i) - '0';
            }
            for (int i = 0; i < b.length(); i++) {
                result[i] += b.charAt(b.length()-1-i) - '0';
            }
            
            // 处理进位
            for (int i = 0; i < len-1; i++) {
                result[i+1] += result[i] / 10;
                result[i] %= 10;
            }
            
            // 去除前导零并输出
            StringBuilder sb = new StringBuilder();
            int start = len-1;
            while (start > 0 && result[start] == 0) start--;
            for (int i = start; i >= 0; i--) {
                sb.append(result[i]);
            }
            System.out.println(sb.toString());
        }
    }
}

def is_legal(s: str) -> bool:
    return s.isdigit()

while True:
    try:
        # 读取输入
        a, b = input().split()
        
        # 判断输入是否合法
        if not is_legal(a) or not is_legal(b):
            print("error")
            continue
        
        # 将字符串转为数字列表，反向存储
        len_max = max(len(a), len(b)) + 1
        result = [0] * len_max
        
        # 从低位开始相加
        for i in range(len(a)):
            result[i] += int(a[-(i+1)])
        for i in range(len(b)):
            result[i] += int(b[-(i+1)])
        
        # 处理进位
        for i in range(len_max - 1):
            result[i+1] += result[i] // 10
            result[i] %= 10
        
        # 去除前导零并输出
        while len(result) > 1 and result[-1] == 0:
            result.pop()
        print(''.join(map(str, result[::-1])))
        
    except EOFError:
        break