用pair存数位之和和原数，重写sort的cmp比较函数即可

#include <iostream>
#include <cstring>
#include <algorithm>
using namespace std;
typedef long long LL;
typedef pair<int, int> PII;
const int N = 1e6+10;
int n,m;
PII a[N];
#define x first
#define y second

int get_num(int x)
{
    int res = 0;
    while(x)
    {
        res += x % 10;
        x /= 10;
    }
    return res;
}

bool cmp(PII a,PII b)
{
    if(a.x != b.x)return a.x < b.x;
    return a.y < b.y;
}

int main()
{
    cin>>n>>m;
    for (int i = 1; i <= n; i ++ )
    {
        int sum = get_num(i);
        a[i] = {sum,i};
    }
    sort(a+1,a+1+n,cmp);
    cout<<a[m].y<<endl;
    return 0;
}