Language: C++

/**
 * code generated by JHelper
 * More info: https://github.com/AlexeyDmitriev/JHelper
 * @author majk
 */

#ifndef MAJK_LIB
#define MAJK_LIB

#include <vector>
#include <stack>
#include <iostream>
#include <fstream>
#include <unordered_map>
#include <unordered_set>
#include <map>
#include <iomanip>
#include <set>
#include <functional>
#include <algorithm>
#include <numeric>
#include <cassert>
#include <cmath>
#include <string>
#include <queue>
#include <array>
#include <bitset>
using namespace std;

#define x first
#define y second
typedef std::pair<int,int> pii; typedef long long ll; typedef unsigned long long ull; typedef unsigned int ui; typedef pair<ui,ui> puu;

template <typename T, typename U> std::istream&operator>>(std::istream&i, pair<T,U>&p) {i >> p.x >> p.y; return i;}
template<typename T>std::istream&operator>>(std::istream&i,vector<T>&t) {for(auto&v:t){i>>v;}return i;}
template <typename T, typename U> std::ostream&operator<<(std::ostream&o, const pair<T,U>&p) {o << p.x << ' ' << p.y; return o;}
template<typename T>std::ostream&operator<<(std::ostream&o,const vector<T>&t) {if(t.empty())o<<'\n';for(size_t i=0;i<t.size();++i){o<<t[i]<<" \n"[i == t.size()-1];}return o;}
template<typename T> using minheap = priority_queue<T, vector<T>, greater<T>>;
template<typename T> using maxheap = priority_queue<T, vector<T>, less<T>>;
ui logceil(ll x) { return x?8*sizeof(ll)-__builtin_clzll(x):0; }

namespace std { template<typename T,typename U>struct hash<pair<T,U>>{hash<T>t;hash<U>u;size_t operator()(const pair<T,U>&p)const{return t(p.x)^(u(p.y)<<7);}}; }
template<typename T,typename F>T bsh(T l,T h,const F&f){T r=-1,m;while(l<=h){m=(l+h)/2;if(f(m)){l=m+1;r=m;}else{h=m-1;}}return r;}
template<typename F> double bshd(double l,double h,const F&f,double p=1e-9){ui r=3+(ui)log2((h-l)/p);while(r--){double m=(l+h)/2;if(f(m)){l=m;}else{h=m;}}return (l+h)/2;}
template<typename T,typename F>T bsl(T l,T h,const F&f){T r=-1,m;while(l<=h){m=(l+h)/2;if(f(m)){h=m-1;r=m;}else{l=m+1;}}return r;}
template<typename F> double bsld(double l,double h,const F&f,double p=1e-9){ui r=3+(ui)log2((h-l)/p);while(r--){double m=(l+h)/2;if(f(m)){h=m;}else{l=m;}}return (l+h)/2;}
template<typename T> T gcd(T a,T b) { if (a<b) swap(a,b); return b?gcd(b,a%b):a; }


template<typename T>class vector2:public vector<vector<T>>{public:vector2(){} vector2(size_t a,size_t b,T t=T()):vector<vector<T>>(a,vector<T>(b,t)){}};
template<typename T>class vector3:public vector<vector2<T>>{public:vector3(){} vector3(size_t a,size_t b,size_t c,T t=T()):vector<vector2<T>>(a,vector2<T>(b,c,t)){}};
template<typename T>class vector4:public vector<vector3<T>>{public:vector4(){} vector4(size_t a,size_t b,size_t c,size_t d,T t=T()):vector<vector3<T>>(a,vector3<T>(b,c,d,t)){}};
template<typename T>class vector5:public vector<vector4<T>>{public:vector5(){} vector5(size_t a,size_t b,size_t c,size_t d,size_t e,T t=T()):vector<vector4<T>>(a,vector4<T>(b,c,d,e,t)){}};


#endif
#ifndef UTIL_H
#define UTIL_H



template <typename T> struct bounded_priority_queue {
	inline bounded_priority_queue(ui X) : A(X), B(0), s(0) {}
	inline void push(ui L, T V) { B = max(B, L); A[L].push(V); ++s; }
	inline const T &top() const { return A[B].front(); }
	inline void pop() { --s; A[B].pop(); while (B > 0 && A[B].empty()) --B; }
	inline bool empty() const { return A[B].empty(); }
	inline void clear() { s = B = 0; for (auto &a: A) a = queue<T>(); }
	inline ui size() const { return s; }
private:
	vector<queue<T>> A; ui B; int s;
};

struct	UnionFind {
	UnionFind(size_t N) : P(N, -1), comp(N) {}
	int find(int x) { while (P[x]> 0){x = P[x]-1;}return x; }
	bool united(int x, int y) { return find(x) == find(y); }
	bool unite(int x, int y) { x=find(x);y=find(y);if(x==y){return false;}--comp;if(P[x]>P[y]){swap(x,y);}P[x]+=P[y];P[y]= x+1;return true;}
	inline ui size(int u) { return -P[find(u)]; }
	vector<int> P;
	size_t comp;
};



#endif


// 15 min
class DUniquePath {
public:
    void solve(istream& cin, ostream& cout) {
       N, M, Q; cin >> N >> M >> Q;
        vector<pii> A, B;
        for (int i = 0; i < Q; ++i) {
            int a, b, c;
            cin >> a >> b >> c;
            (c?B:A).emplace_back(a,b);
        }

        UnionFind UF(N);
        for (pii a: A) UF.unite(a.x, a.y);
        for (pii b: B) if (UF.united(b.x, b.y)) {
            cout << "No\n";
            return;
        }


        if (M > N - UF.comp + ll(UF.comp) * ll(UF.comp - 1) / 2) {
            cout << "No\n";
            return;
        }

        if (M == N-1 && !B.empty()) {
            cout << "No\n";
            return;
        }

        cout << "Yes\n";
    }
};


int main() {
	ios_base::sync_with_stdio(false); cin.tie(nullptr); cout.tie(nullptr);
	DUniquePath solver;
	std::istream& in(std::cin);
	std::ostream& out(std::cout);
	solver.solve(in, out);
    return 0;
}


Compiler output:
a.cc: In member function 'void DUniquePath::solve(std::istream&, std::ostream&)':
a.cc:93:8: error: 'N' was not declared in this scope
   93 |        N, M, Q; cin >> N >> M >> Q;
      |        ^
a.cc:93:11: error: 'M' was not declared in this scope
   93 |        N, M, Q; cin >> N >> M >> Q;
      |           ^
a.cc:93:14: error: 'Q' was not declared in this scope
   93 |        N, M, Q; cin >> N >> M >> Q;
      |              ^