C++ 实现MST kruskal's algorithm

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#include<iostream>
#include<vector>
#include<list>
#include<iomanip>
#include<algorithm>

using namespace std;

enum{ INF = INT_MAX };

struct Edge{
	int from;
	int to;
	int Wgt;
	
	Edge(int _from, int _to, int _Wgt = INF) :
		from(_from), to(_to), Wgt(_Wgt) {}
	
	bool operator <(const Edge & rhs) const {
		return Wgt < rhs.Wgt;
	}
};

int root(vector<int> & Fr, int vrt) {
	while (Fr[vrt] != -1) {
		vrt = Fr[vrt];
	}
	return vrt;
}

bool Kruskal(vector<vector<int> > & G, vector<int> & Fr) {
	//init forest.
	vector<int>(G.size(), -1).swap(Fr);
	
	//build Edge list;
	list<Edge> EL;
	for (int i = 0; i < G.size(); ++i) {
		for (int j = 0; j < G.size(); ++j) {
			if (G[i][j] != INF && G[i][j] != 0)
				EL.push_back(Edge(i, j, G[i][j]));
		}
	}
	EL.sort();	//ascending order.

	//span
	int Ecnt = 0;
	while (Ecnt < G.size() - 1 && !EL.empty()) {
		//extract edge.
		Edge e(EL.front());
		EL.pop_front();

		if (root(Fr, e.from) != root(Fr, e.to)) {
			++Ecnt;	//append edge.
			Fr[e.to] = e.from;	//merge tree.
		}
	}

	if (Ecnt < G.size() - 1) {
		cout << "Not connected graph." << endl;
		return false;
	}
	else
		return true;
}

int main(void) {
	cout << "Kruskal algorithm." << endl;
	int n, m;
	while (cin >> n >> m) {
		vector<vector<int> > G(n, vector<int>(n, INF));
		for (int i = 0; i < n; ++i) G[i][i] = 0;

		//input edges.
		for (int i = 0; i < m; ++i) {
			int s, t;
			cin >> s >> t;
			cin >> G[s][t];
		}

		//display matrix.
		cout << "Adj: " << endl;
		for (int i = 0; i < G.size(); ++i) {
			for (int j = 0; j < G.size(); ++j) {
				cout << " " << setw(3) << G[i][j];
			}
			cout << endl;
		}
		cout << endl;

		vector<int> Fr;
		
		if (Kruskal(G, Fr)) {
			cout << "Parenthoods of the spanning tree:" << endl;
			for (int i = 0; i < Fr.size(); ++i) {
				cout << "Vertex: " << i << "   Parent: " << Fr[i] << endl;
			}
		}
	}
	system("pause");
	return 0;
}

输入样例:

8 32
0 1 10
1 0 10
0 3 10
3 0 10
0 5 14
5 0 14
0 7 11
7 0 11
1 2 10
2 1 10
1 4 7
4 1 7
1 6 7
6 1 7
2 3 11
3 2 11
2 5 9
5 2 9
2 7 8
7 2 8
3 4 12
4 3 12
3 6 15
6 3 15
4 5 13
5 4 13
4 7 16
7 4 16
5 6 13
6 5 13
6 7 12
7 6 12

C++ 实现MST kruskal's algorithm

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原文地址：http://blog.csdn.net/qq_21555605/article/details/46659527