PAT题集 L1-025 正整数A+B (15 分)测试点3错误求解答

#include <iostream>
#include <string.h>
using namespace std;
int isNum(char str[]){
	int i;
	for(i=0;i<strlen(str);i++){
		if(!(str[i]>='0'&&str[i]<='9'||i==0&&str[0]=='+')){
			return -1;
		}
	}
	if(i==strlen(str)&&atoi(str)<=1000) return atoi(str); 
	return -1;
}
int main(int argc, char *argv[])
{
    char c;
	char A[8000],B[8000];
	int a,b;
	cin>>A;
	if((c=getchar())=='\n'){
		b=isNum(A);
		a=-1;
		goto LOOP;
	}
	cin>>B;
	a=isNum(A);
 	b=isNum(B);
 	LOOP:
	if(a>0)
		cout<<a;
	else{
		cout<<"?";
	} 
	cout<<" + ";
	if(b>0)
		cout<<b;
	else{
		cout<<"?";
	}
	cout<<" = ";
	if(a>0&&b>0){
		cout<<a+b;
	}else
		cout<<"?";
	return 0;
}

测试点3错误，哪个输入有误？最好贴出来，另外，给一个参考一下。

#include<iostream>
#include<string>
using namespace std;
int main()
{
	string a;
	getline(cin, a);
	int m = 0, n = 0;//所有字符串的和
	int x = 0, y = 0;//只有数字的和
	int i = 0;
	for (i; i<a.length(); i++)
	{
		if (a[i] == ' ') break;
		m = m * 10 + (a[i] - '0');
		if (a[i] >= '0'&&a[i] <= '9')
		{
			x = x * 10 + (a[i] - '0');
		}
	}
	for (int j = i + 1; j<a.length(); j++)
	{
		//if(a[j]==' ') break; 
		n = n * 10 + (a[j] - '0');
		if (a[j] >= '0'&&a[j] <= '9')
		{
			y = y * 10 + (a[j] - '0');
		}
	}
	if (m <= 1000 && m >= 1 && m == x)
		cout << m;
	else
		cout << "?";
	cout << " + ";
	if (n <= 1000 && n >= 1 && n == y)
		cout << n;
	else
		cout << "?";
	cout << " = ";
	if (n <= 1000 && n >= 1 && m <= 1000 && m >= 1 && m == x&&n == y)
		cout << m + n;
	else
		cout << "?";
	return 0;