Python(2.7.3) 解法, 执行用时: 455ms, 内存消耗: 6372K, 提交时间: 2019-04-14 13:10:51

import math
def nth(n):
    if n<=9:return n
    tmp_sum = 9
    num = 9
    num2 = 1
    while n>=tmp_sum:
        if n==tmp_sum:return 9
        num*=10
        num2+=1
        tmp_sum+=(num*num2)
    tmp_sum -= (num*num2)
    n = n-tmp_sum
    c1 = n/num2
    c2 = n%num2
    if c2==0:return (num/9+c1-1)%10
    return int(str(num/9+c1)[c2-1])

n = int(raw_input().strip())
for i in range(n):
    x = int(raw_input().strip())
    print nth(x)

C++14(g++5.4) 解法, 执行用时: 73ms, 内存消耗: 2588K, 提交时间: 2019-04-19 16:09:04

#include<iostream> 
#include<cstring>
#include<string>
#include<cstdio>
using namespace std;
int main(){
	int gt;
	long long p,w,t;
	scanf("%d",&gt);
	while(gt--){
		
		scanf("%lld",&p);
		 w=1,t=9;
		while(p>t*w){
			p-=t*w;
			t*=10;
			w++;
		}
		long long m=p%w;
		t=t/9;
		long long s;
		if(m==0){
			s=t+p/w-1;
			m=w;
		}
		else {
			s=t+p/w;
		}
		char ss[100];
		sprintf(ss,"%lld",s);
		printf("%c\n",ss[m-1]);
	}
	return 0;
}

C++11(clang++ 3.9) 解法, 执行用时: 329ms, 内存消耗: 640K, 提交时间: 2020-02-26 22:53:59

#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
int main()
{
	int T;
	scanf("%d",&T);
	while(T--)
	{
		ll p;
		cin>>p;
		ll len=1;
		ll num=9;
		while(p>len*num)
		{
			p-=len*num;
			len++;
			num*=10;
		}
		ll number=num/9+(p-1)/len;
		ll loc=len-(p-1)%len;
		while(--loc) number/=10;
		cout<<number%10<<endl;
	}
	return 0;
}

Python3(3.5.2) 解法, 执行用时: 1658ms, 内存消耗: 3692K, 提交时间: 2019-04-14 16:45:18

n = int(input())
def find(n):
    _len = 1
    cnt = 9
    start = 1
    while n > _len * cnt:
        n -= _len * cnt
        _len += 1
        cnt *= 10
        start *= 10
    start += (n - 1) // _len
    return int(str(start)[(n - 1) % _len])
for i in range(n):
    print(find(int(input())), sep='', end='\n')