求大佬看看，学的第一个题解思路，为啥c运行不起来

#include<stdio.h>
#include<string.h>
char ar[100];
char br[10];

int main()
{
    int n;
    scanf("%d",n);
    int u,v;
    char y;
    for(int i=0;i<n;i++)
    {
        scanf("%s",br);
        if(br[0]>='a'&&br[0]<='z')
        {
            scanf("%d%d",&u,&v);
            y=br[0];
        }
        else
        {
            sscanf(br,"%d",&u);
            scanf("%d",&v);
        }
        memset(ar,0,sizeof(ar));
        if(y=='a')
        {
            sprintf(ar,"%d+%d=%d",u,v,u+v);
        }
        else if(y=='b')
        {
            sprintf(ar,"%d-%d=%d",u,v,u-v);
        }
        else if(y=='c')
        {
            sprintf(ar,"%d*%d=%d",u,v,u*v);
        }
        printf("%s\n",ar);
        printf("%d",strlen(ar));
    }
    return 0;
}