小米 oj 找到第N个数字||

Mycode:

#include<iostream>
#include<stdio.h>
#include<string.h>
using namespace std;
typedef long long ll;
string now;
ll n;
int len(ll m)
{
    if(m<=9)return 1;
    else if(m<=99)return 2;
    else if(m<=999)return 3;
    else if(m<=9999)return 4;
    else if(m<=99999)return 5;
    else if(m<=999999)return 6;
    else if(m<=9999999)return 7;
    else if(m<=99999999)return 8;
    else return 9;
}
int main()
{
    while(~scanf("%lld",&n))
    {
        now="";
        ll m=1;
        ll sum=0;
        while(1)
        {
            now+=std::to_string(m);
            m++;
            if(sum+now.size()<n)
            {
                sum+=now.size();
            }
            else if(sum+now.size()==n) 
            {
                cout<<now[now.size()-1]<<endl;
                break;
            }
            else 
            {
                ll pos=n-sum;
                cout<<now[pos-1]<<endl;
                break;
            }
        }
    }
    return 0;
}