Cod sursa(job #2098442)

Utilizator sandupetrascoPetrasco Sandu sandupetrasco Data 2 ianuarie 2018 20:09:00
Problema Radiatie Scor 30
Compilator cpp Status done
Runda Arhiva de probleme Marime 1.86 kb
#include <bits/stdc++.h>

#define pb push_back 
#define x first 
#define y second 
#define MOD 1000000007

using namespace std;
typedef long long ll;
typedef pair< int , int > PII;
const int dirx[] = {-2,-1,1,2, 1, -1};
const int diry[] = {0,1,1,0, -1, -1};
inline void debugMode() {
    #ifndef ONLINE_JUDGE
    freopen("radiatie.in", "r", stdin);
    freopen("radiatie.out", "w", stdout);
    #endif
}

int n, m, k, U[1 << 18], Lvl[1 << 18], F[1 << 18];
vector < int > V[1 << 18];
unordered_map < int , int > M;

PII A[1 << 18];

int Hash(int x, int y){
	return x * (1 << 18) + y;
}

void make_DFS(int x, int fath, int lvl){
	Lvl[x] = lvl;
	F[x] = fath;
	for (auto it : V[x])
		if (it != fath)
			make_DFS(it, x, lvl + 1);
}


int get_LCA(int x, int y){
	int mx = 0;

	while (Lvl[x] > Lvl[y]){
		mx = max(mx, M[Hash(x, F[x])]);
		x = F[x];
	}

	while (Lvl[y] > Lvl[x]){
		mx = max(mx, M[Hash(y, F[y])]);
		y = F[y];
	}

	while (Lvl[x] && Lvl[y] && x != y){
		mx = max(mx, M[Hash(x, F[x])]);
		mx = max(mx, M[Hash(y, F[y])]);
		x = F[x], y = F[y];
	}

	return mx;
}

int find(int x){ return (U[x] == x ? x : U[x] = find(U[x])); }
void unite(int x, int y){ U[find(y)] = U[find(x)]; }

int main(){
	debugMode();
	ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
	cin >> n >> m >> k;
	for (int i = 1; i <= n; i++) U[i] = i;

	for (int i = 1, x; i <= m; i++){
		cin >> A[i].x >> A[i].y >> x;
		if (!M[Hash(A[i].x, A[i].y)] || (M[Hash(A[i].x, A[i].y)] > x)) M[Hash(A[i].x, A[i].y)] = x;
		M[Hash(A[i].y, A[i].x)] = M[Hash(A[i].x, A[i].y)];
	}

	sort(A + 1, A + m + 1, [&](PII a, PII b){return M[Hash(a.x, a.y)] < M[Hash(b.x, b.y)];});

	for (int i = 1; i <= m; i++)
		if (find(A[i].x) != find(A[i].y)){
			unite(A[i].x, A[i].y);
			V[A[i].x].pb(A[i].y);
			V[A[i].y].pb(A[i].x);
	}
	make_DFS(1, 0, 1);

	for (int i = 1, x, y; i <= k; i++){
		cin >> x >> y;
		cout << get_LCA(x, y) << "\n";
	}


	return 0;
}