当求n mod m,n很大,但是m又在int范围内时将大数写成以下形式:如1234 = ((1*10+2)*10+3)*10+4 ,然后每步取余,所以有:
/*用str存n*/
ll qmod(){
int len = strlen(str);
long long ans = 0;
for(int i = 0;i < len;i++){
ans = (long long)(((long long)ans*10+str[i]-'0')%mod);
}
return ans;
}
/*用str存n*/
ll qmod(){
int len = strlen(str);
long long ans = 0;
for(int i = 0;i < len;i++){
ans = (long long)(((long long)ans*10+str[i]-'0')%mod);
}
return ans;
}