POJ 1019, Number Sequence

Time Limit: 1000MS  Memory Limit: 10000K
Total Submissions: 17288  Accepted: 4563

Description
A single positive integer i is given. Write a program to find the digit located in the position i in the sequence of number groups S1S2...Sk. Each group Sk consists of a sequence of positive integer numbers ranging from 1 to k, written one after another.
For example, the first 80 digits of the sequence are as follows:
11212312341234512345612345671234567812345678912345678910123456789101112345678910

 

Input
The first line of the input file contains a single integer t (1 ≤ t ≤ 10), the number of test cases, followed by one line for each test case. The line for a test case contains the single integer i (1 ≤ i ≤ 2147483647)

 

Output
There should be one output line per test case containing the digit located in the position i.

 

Sample Input
2
8
3

 

Sample Output
2
2

 

Source
Tehran 2002, First Iran Nationwide Internet Programming Contest

---

// POJ1019.cpp : Defines the entry point for the console application.
//

#include <iostream>
#include <sstream>
using namespace std;
inline int getlen(int i)
{
    if (i < 10) return 1;
    else if (i < 100) return 2;
    else if (i < 1000) return 3;    
    else if (i < 10000) return 4;    
    else if (i < 100000) return 5;
    return 0;
}
inline char getchar(int num, int p)
{
    stringstream ss;
    ss << num;
    string s;
    ss >> s;
    return s[p-1];
}
int main(int argc, char* argv[])
{
    //init table
    const int SIZE = 40000;
    __int64 sum[SIZE];
    sum[0]=0;

    for(int i = 1;i < SIZE;++i)
        sum[i]=sum[i-1]+getlen(i);

    for(int i = 1; i < SIZE; ++i)
        sum[i] +=sum[i-1];

    int cases;
    scanf("%d", &cases);
    __int64 num;
    for (int c = 0; c < cases; ++c)
    {
        scanf("%I64d", &num);

        // Kth group
        int k = 1;
        while(sum[k] < num) ++k;
        
        //posth character of number i
        int pos = num - sum[k-1];
        int i=1;
        while(pos-getlen(i)> 0) pos -= getlen(i), ++i;

        cout << getchar(i,pos) << endl;
    }

    return 0;
}