广工赛-hdu6468构造十叉树

#include<bits/stdc++.h>
using namespace std;
#define maxn 1000005
int size[maxn],k,n,th,ans,flag;
void dfs(int i){
        if(flag)return;
    size[i]=1;
    th++;
    if(th==k)ans=i,flag=1;

    //cout<<i<<endl;
    if(i==0){
        for(int j=1;j<=9;j++)
            if(j<=n)dfs(j);
    }
    else {
        for(int j=0;j<=9;j++){
            int tmp=i*10+j;
            if(tmp<=n){
                dfs(tmp);
                size[i]+=size[tmp];
            }    
            else return;
        }
    }
}
int main(){
    int t;
    cin>>t;
    while(t--){
        th=-1;flag=0;
        scanf("%d%d",&n,&k);
        dfs(0);
        cout<<ans<<endl;
    }
}