历届试题 小数第n位(小技巧)

#include <stdio.h>
#include <iostream>
#include <algorithm>
using namespace std;
long long a,b,n;
int main(){
    scanf("%I64d %I64d %I64d", &a, &b, &n);
    long long t = a % b;
    if(t == 0){
        cout<<"000";
        return 0;
    }
    int count = 0;
    int flag = 0;
    while(--n){
        if(t == 0)
            break;
        t = t * 10;
        t = t % b;
        count++;
        if(t == a % b)
            n = n % count;
    }
    if(!t)
        cout<<"000";
    else{
        t = t * 10;
        cout<< t / b;
        t = t % b;
        
        t = t * 10;
        cout<< t / b;
        t = t % b;
        
        t = t * 10;
        cout<< t / b;            
    }
    return 0;
}