LAST DIGIT 2 SPOJ

5699. The last digit re-visited

Problem code: LASTDIG2




#include<stdio.h>
#include<string.h>
int main()
{
char str[1005];
unsigned long long int b,a,ans,len,t;
scanf("%llu",&t); 
while(t--){
scanf("%s",str);
scanf("%llu",&b);
 len=strlen(str);
//printf("%s\n",str); 
a=str[len-1]-'0'; 
if(b==0&&a!=0) ans=1; 
else{
if(a==0){ ans=0; goto end;}
if(a==5) {ans=5; goto end;}
switch(b%4){
case 0: ans=a%2!=0? 1:6;
break;
case 1: ans=a;
break;
case 2: ans=a*a%10;
break;
default : ans=a*a*a%10;
break; 
}
}
end :
printf("%llu\n",ans);
}
return 0;
}