POJ1019-Number Sequence-数数。。

#include <cstdio>
#include <algorithm>
#include <cmath>

using namespace std;

int T,N,ans;

int getbit(int x)
{
    int rtn = 0;
    while(x)
    {
        x/=10;
        rtn++;
    }
    return rtn;
}

int main()
{
    scanf("%d",&T);
    while(T--)
    {
        scanf("%d",&N);
        int cur = 1,cnt = 1;;
        while(true)
        {
            if(N <= cur) break;
            N -= cur;
            cnt++;
            cur += getbit(cnt);
        }
        //printf("N=%d cur=%d cnt=%d\n",N,cur,cnt);
        cur = 1,cnt = 1;
        while(true)
        {
            if(N <= cur) break;
            N -= cur;
            cnt++;
            cur = getbit(cnt);
        }
        //printf("N=%d cur=%d cnt=%d\n",N,cur,cnt);

        if(cur == N) ans = cnt%10;
        else ans = (int)(cnt/pow(10,cur-N)) % 10;
        printf("%d\n",ans);
    }
}