进位统计

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

int main()
{
    char a[10],b[10];
    int len1,len2,c,n;
    while(scanf("%s %s",&a,&b)!=EOF)
    {
        if(!strcmp(a,"0")&&!strcmp(b,"0")) break;
        len1=strlen(a);
        len2=strlen(b);
        len1--;
        len2--;
        for(c=0,n=0;len1>=0&&len2>=0;len1--,len2--)
        {
            if(a[len1]+b[len2]+c-'0'<='9'&&a[len1]+b[len2]+c-'0'>='0')
                c=0;
            else{
                c=1;
                n++;
            }
        }
        if(len1>0&&a[len1]+c>'9') n++;
        else if(len2>0&&b[len2]+c>'9') n++;
        if(n==0) printf("NO carry operation.\n");
        else if(n==1) printf("1 carry operation.\n");
        else printf("%d carry operations.\n",n);
    }
    return 0;
}