输入n后回车出现一个0

#include<stdio.h>
#include<string.h>

 
int main()
{
    char a[10];
    int n,j;
    scanf("%d",&n);
    while(n--)
    {
     gets(a);
     int i,h=0;
     for(i=0 ; a[i]!='\0' ; i ++)
     {
         if(a[i] == 'I')h =h+1;
         if(a[i] == 'V')h=h+5;
         if(a[i] == 'X')h =h+10;
         if(a[i] == 'L')h =h+50;
         if(a[i] == 'C')h =h+100;
         if(a[i] == 'D')h =h+ 500;
         if(a[i] == 'M')h =h+ 1000;
     }
     if(strstr(a,"IV"))h =h-2;
     if(strstr(a,"IX"))h =h-2;
     if(strstr(a,"XL"))h =h-20;
     if(strstr(a,"XC"))h =h-20;
     if(strstr(a,"CD"))h =h-200;
     if(strstr(a,"CM"))h =h-200;
     printf("%d\n",h);
    }
     return 0;
}

因为你输入n的值3后，按回车键了。这样gets(a)实际自动接收了换行符，不需要你再输入内容。这样导致a字符串是个空串，最后h没有赋予任何值，还是初始的0，所以输出了0
修改办法： scanf("%d",&n);后增加一句getchar();就可以了，把换行符接收掉

get(a)读取到的a就是回车键啊，不等于你任何一个if条件，h=0不是正常的结果吗

#include<stdio.h>
#include<string.h>


int main()
{
    char a[10];
    int n, j;
    scanf("%d", &n);
    while (n--)
    {
        getchar();
        gets_s(a);
        int i, h = 0;
        for (i = 0; a[i] != '\0'; i++)
        {
            if (a[i] == 'I')h = h + 1;
            if (a[i] == 'V')h = h + 5;
            if (a[i] == 'X')h = h + 10;
            if (a[i] == 'L')h = h + 50;
            if (a[i] == 'C')h = h + 100;
            if (a[i] == 'D')h = h + 500;
            if (a[i] == 'M')h = h + 1000;
        }
        if (strstr(a, "IV"))h = h - 2;
        if (strstr(a, "IX"))h = h - 2;
        if (strstr(a, "XL"))h = h - 20;
        if (strstr(a, "XC"))h = h - 20;
        if (strstr(a, "CD"))h = h - 200;
        if (strstr(a, "CM"))h = h - 200;
        printf("%d\n", h);
    }
    return 0;
}

先初始化一下数组：

char a[10]={'\0'};

scanf("%d",&n);后增加一句getchar()
将回车接收