poj 1019

二分，模拟。

#include <iostream>
#include <cstdio>
#include <iomanip>
#include <string>
#include <cstdlib>
#include <cstring>
#include <queue>
#include <set>
#include <vector>
#include <map>
#include <algorithm>
#include <cmath>
#include <stdlib.h>
#include <stdio.h>

#define INF 0x3f3f3f3f
#define LINF 0x3f3f3f3f3f3f3f3f
#define ll long long
#define ull unsigned long long
#define uint unsigned int
#define l(x) x<<1
#define r(x) x<<1|1
#define ms(a,b) memset(a,b,sizeof(a))

using namespace std;

unsigned int d1[31269],d2[31269];

int t, n,res;

int main(){
	d1[1] = 1;
	d2[1] = 1;
	for (int i = 2; i < 31269; i++) {
		d1[i] = d1[i - 1] + (int)log10((double)i) + 1;
		d2[i] = d2[i - 1] + d1[i];
	}

	cin >> t;
	while (t--) {
		cin >> n;
		int i = upper_bound(d2, d2 + 31269, n) - d2;
		if (n == d2[i - 1])
			i--;

		int pos = n - d2[i-1];

		int len = 0;
		for (i = 1; len < pos; i++)
			len += (int)log10((double)i) + 1;

		cout << ((i - 1) / (int)pow((double)10, len - pos) % 10) << endl;
	}

	return 0;
}