剑指offer 面试题44：数字序列中某一位的数字

#include <iostream>
#include <vector>

using namespace std;

int digitAtIndex(int index);

int main()
{
    int ans = digitAtIndex(9);
    cout << ans << endl;

    return 0;
}

int digitAtIndex(int index)
{
    int length = 9;
    int digit = 1;
    int num = 9;
    while(index > length) {
        index -= length;
        cout << index << endl;
        digit += 1;
        num *= 10;
        length = digit * num;
    }

    int q = index/digit;
    int remainder = index%digit;
    //cout << q << " " << remainder << endl;

    int base = 1;
    for(int i = 1; i < digit; ++i) {
        base *= 10;
    }
    int ans;
    if(remainder == 0) {
        int temp = base + q - 1;
        ans = temp%10;
    } else {
        int temp = base + q;
        vector<int> v;
        while(temp != 0) {
            int r = temp%10;
            v.push_back(r);
            temp = temp/10;
        }
        /*
        for(int elem : v) {
            cout << elem << " ";
        }
        cout << endl;
        */
        ans = v[digit-remainder];
    }

    return ans;
}