URI 1610 Dudu Service Maker

/**
  *  @Author: Pranta Sarker
  *
  **/


// Cycle finding Problem
// Used Algorithm: DFS

#include<bits/stdc++.h>

using namespace std;

#define fast ios_base::sync_with_stdio(0)
#define bfast cin.tie(0)
#define outs(x) cout << x << " "
#define outn(x) cout << x << "\n"
#define sf scanf
#define pf printf
#define pfn(x , k) printf(k , x)
#define nl puts("")
#define psb push_back
#define mset(c,v) memset(c , v , sizeof c)
#define loop0(n) for(int i=0; i<n; i++)
#define loop1(n) for(int i=1; i<=n; i++)
#define mpair(x , y) make_pair(x , y)
#define all(x) x.begin(), x.end()
#define pi acos(-1.0)
#define psb push_back
#define clr clear()

typedef unsigned long long ull;
typedef long long LL;
typedef vector<int>vii;
typedef vector<LL>vll;
typedef vector<string>vs;
typedef map<int, int>mpii;
typedef map<string, int>mpsi;
typedef map<char, int>mpci;
typedef map<LL, LL>mpll;

const int mod = 1000007;
const int high = 30002;
const int gray = 1;
const int black = -1;
const int white = 0;

bool cycle = false;

vii adj[high];
int color[high];

void CLR()
{
    loop0(high)
    {
        adj[i].clr;
        color[i] = white;
    }

    cycle = false;
}

void DFS(int u)
{
    if(color[u] == gray)
    {
        cycle = true;
        return;
    }

    color[u] = gray;

    for(int i=0; i<adj[u].size(); i++)
    {
        int v = adj[u][i];

        if(color[v] == white)
        {
            DFS(v);
        }

        else if(color[v] == gray)
        {
            cycle = true;
            return;
        }
    }

    color[u] = black;
}

int main()
{
    fast;
    int test;
    cin >> test;
    while(test--)
    {
        CLR();

        int i , N , M, u , v;
        cin >> N >> M;

        for(i=0; i<M; i++)
        {
            cin >> u >> v;

            adj[u].psb(v);
        }

        for(i=1; i<=N; i++)
        {
            if(color[i] == white)
            {
                DFS(i);
            }

            else break;
        }

        if(cycle) cout << "SIM\n";
        else cout << "NAO\n";
    }

    return 0;
}