按照《深入浅出》基础篇的思路写的，样例一摸一样，但是WA

#define _CRT_SECURE_NO_WARNINGS
#include <iostream>
#include <cstdio>
#include <string>
#include <cstring>
using namespace std;
int main()
{
    int n;
    char lastsign;
    char s[30];
    char s2[30];
    int a, b;
    cin >> n;
    getchar();
    getchar();
    int sum;
    while (n-- > 0) {
        fgets(s, sizeof(s), stdin);
        if (s[0] == 'a' || s[0] == 'b' || s[0] == 'c') {
            lastsign = s[0]; s[0] = ' ';//为了使下面的scanf能够正常输入;
        }
        sscanf(s, "%d %d", &a, &b);
        switch (lastsign) {
        case 'a': 
            sum = a + b; 
            sprintf(s2, "%d+%d=%d",a,b, sum); break;//break别忘了
        case 'b':
            sum = a - b; 
            sprintf(s2, "%d-%d=%d", a, b, sum); break;
        case 'c': 
            sum = a * b;
            sprintf(s2, "%d*%d=%d", a, b, sum); break;
        }
        printf("%s\n", s2);
        cout << strlen(s2) << endl;

    }
    return 0;
}

好像真的没什么问题啊 要疯了