Poj 1019

传送门：http://poj.org/problem?id=1019

主要是找数学规律

然后用好pow和log函数，由于数组过大，数组的类型用unsigned

#include<iostream>
#include<cmath>
using namespace std;

int t;
int k;
int n;
unsigned a[31269];
int m;

int main(){
    cin>>t;
    a[0]=0;
    for(int i=1;i<31269;i++){
        a[i]=a[i-1]+int(log10(double(i)))+1;
    }//打表
    while(t--){
        cin>>k;
        n=1;
        while(a[n]<k){
            k-=a[n];
            n++;
        }
        m=1;
        int q=int(log10(double(m)))+1;
        while(q<k){
            k-=q;
            m++;
            q=int(log10(double(m)))+1;
        }
        cout<<m/int(pow(double(10),double(q-k)))%10<<endl;

    }
}