#include<iostream>
#include<vector>
#include<algorithm>
using namespace std;
int t;
int main(){
    cin>>t;
    for(int k=1;k<=t;k++){
        int n,m;
        cin>>n>>m;
        vector<vector<int>> a(n+1);
        for(int i=0;i<m;++i){
            int u,v;
            cin>>u>>v;
            a[u].push_back(v);
        }
        for(int i=1;i<=n;++i){
            if (a[i].empty())cout<<endl;
            else{
                sort(a[i].begin(),a[i].end());
                for (int v:a[i]){
                    cout<<v<<" ";
                }
                cout<<endl;
            }
        }
    }
    return 0;
}

这个代码在DEV-C++一直报错（vector<vector> a(n+1);）QWQ有大佬能解释一下吗？题目能过的