10706 - Number Sequence----------思维题（比较难以想到）暴力搜就行

#include<cstdlib>
#include<iostream>
#include<cstdio>
#include<cmath>
#include<cstring>
#include<algorithm>
#include<set>
#include<stack>
#include<map>
#include<list>
#include<queue>
#include<vector>
#define LL long long
#define inf 0x7fffffff
#define E 1e-9
#define M 100
#define N 100005
using namespace std;
int m,n,t;
LL a
;
int wei(int k)
{
    int ans=0;
    while(k)
    {
        ans++;
        k/=10;
    }
    return ans;
}
void init()
{
    a[1]=1;
    a[0]=0;
    int last=1;
    for(int i=2; i<N; i++)
    {
        last+=wei(i);
        a[i]=a[i-1]+last;
    }
}
void find(int n)
{
    int sub;
    for (int i=1; i<N; ++i )
        if(a[i]>=n)
        {
            sub=i-1;
            break;
        }
    n-=a[sub];
    int last=0;
    for (int i=1; i<=sub+1; ++i )
    {
        last+=wei(i);
        if(last>=n)
        {
            n-=(last-wei(i));
            last=i;
            break;
        }
    }
    n=wei(last)-n;
    printf("%d\n",(last/(int)pow(10,n))%10);
}
int main()
{
#ifndef ONLINE_JUDGE
    freopen("ex.in","r",stdin);
#endif
    scanf("%d",&t);
    init();
    while(t--)
    {
        scanf("%d",&n);
        find(n);
    }
    return 0;
}