RT 求调，TLE一页了

#include <bits/extc++.h>

using namespace std;
using namespace __gnu_pbds;
using namespace __gnu_cxx;

inline long long read()
{
    long long x = 0, f = 1;
    char ch = getchar();
    while (!isdigit(ch))
    {
        if (ch == '-')
        {
            f = -1;
        }
        ch = getchar();
    }
    while (isdigit(ch))
    {
        x = (x << 1) + (x << 3) + (ch ^ 48);
        ch = getchar();
    }
    return x * f;
}

inline void write(long long x)
{
    if (x < 0)
        putchar('-'), x = -x;
    if (x > 9)
        write(x / 10);
    putchar(x % 10 + 48);
}

typedef long long ll;
typedef unsigned long long ull;
typedef long double ld;

ll n, m;

vector<set<ll>> G;

void init()
{
    n = 0, m = 0;
    G.resize(0);
}

void solution()
{
    init();

    // n = read();
    // m = read();

    scanf("%lld",&n);
    scanf("%lld",&m);

    G.resize(n + 1);

    for (ll i = 1; i <= m; i++)
    {
        // ll u = read();
        // ll v = read();

        ll u=0,v=0;
        scanf("%lld",&u);
        scanf("%lld",&v);

        G[u].insert(v);
    }

    for (ll i = 1; i <= m; i++)
    {
        if (G[i].empty())
        {
            // cout<<endl;
            // cout<<'\n';
            // puts("");
            putchar('\n');
            continue;
        }
        for (auto j : G[i])
        {
            // cout<<j<<" ";
            // printf("%lld ", j);
            write(j);
            putchar(' ');
        }
        // cout<<endl;
        // cout << '\n';
        putchar('\n');
    }
}

int main()
{
    ll T = 0;
    // T = read();
    scanf("%lld",&T);
    for (ll i = 0; i < T; i++)
    {
        solution();
    }

    // Debug
    // int Debuger=0;
    // cin>>Debuger;
    return 0;
}