poj 1019 Number Sequence

// 题意: 一串有规律的数字，
// 11212312341234512345612345671234567812345678912345678910123456789101112345678910...
// 拆分出来就是 11 212 3123 41234 5… 问第i位数字是多少,i ≤ 2147483647

#include <iostream>
#include <string.h>
using namespace std;
int count[35000];
int digit(int n)    //返回n的位数
{
    int d = 0;
    while(n)
    {
        n /= 10;
        d++;
    }
    return d;
}
int main()
{
    int cases,i, j,ans;
    long long n;
    for (i = 1; i < 35000; i++) 
        count[i] = count[i - 1] + digit(i);
    cin>>cases;
    while(cases--)
    {
        cin>>n;
        i = 0;
        while (n >= count[i])
        {
            n -= count[i];
            i++;
        }
        if (n==0)
            ans= (i - 1) % 10;
        else 
        {
            i = 0;
            while(count[i] <= n)
                i++;
            n -= count[i - 1];    //count[i-1]<=n<count[i]
            if (n==0)
                ans = (i - 1) % 10;
            else 
            {
                j = digit(i);
                while(n++ < j)
                {
                    i /= 10;
                }
                ans = i % 10;
            }    
        }    
        cout<<ans<<endl;
    }
    return 0;
}