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# Kruskal algorithm

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Source code Kruskal algorithm by Tran Dan Thu

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### Kruskal algorithm

1. 1. // File: Kruskal.h-------------------------------------------------------------#ifndef _MY_KGRAPH_H#define _MY_KGRAPH_H#include <iostream>#include <fstream>#include <vector>#include <algorithm>using namespace std;class Edge { int v1, v2; float w;public: Edge(int v1=0, int v2=0, float w=0); int getV1(); int getV2(); float getW(); ostream& Show(ostream& outDev) const; friend bool operator < (const Edge& e1, const Edge& e2); friend bool operator == (const Edge& e1, const Edge& e2); friend istream& operator >> (istream&, Edge&); friend ostream& operator << (ostream&, const Edge&);};class KruskalAlgo { vector<int> Label; vector<Edge> Edges; vector<Edge> T; int nVer; void UpdateLabels(int v1, int v2); void InitAlg();public: void LoadEdges(istream& inDev) ; bool LoadEdges(char* fName) ; int RunAlg(); void ShowT(ostream& outDev);};#endif// end of File: Kruskal.h-------------------------------------------------------
2. 2. // File Kruskal.cpp-----------------------------------#include "Kruskal.h"// Methods and operators for Edge classEdge::Edge(int v1, int v2, float w){ this->w=w; this->v1=v1; this->v2=v2;}int Edge::getV1() { return v1;}int Edge::getV2() { return v2;}float Edge::getW() { return w;}ostream& Edge::Show(ostream& outDev) const { outDev << v1 << "----"<< v2 << " ; w = " << w; return outDev;}bool operator < (const Edge& e1, const Edge& e2){ return e1.w < e2.w;}bool operator == (const Edge& e1, const Edge& e2){ return e1.w == e2.w;}istream& operator >> (istream& inDev, Edge& e){ inDev >> e.v1 >> e.v2 >> e.w; return inDev;}ostream& operator << (ostream& outDev, const Edge& e){ return e.Show(outDev);}
3. 3. // Methods and operators for KruskalAlgo classvoid KruskalAlgo::LoadEdges(istream& inDev){ int nE; Edge e; inDev >> nVer >> nE; for (int i=0; i<nE; i++){ inDev >> e; Edges.push_back(e); }}bool KruskalAlgo::LoadEdges(char* fName){ ifstream inFile(fName); if (inFile){ LoadEdges(inFile); return true; } return false;}void KruskalAlgo::UpdateLabels(int v1, int v2){ if (v1<0 || v1 >= nVer || v2<0 || v2>=nVer){ return; } int minLabel = Label[v1], maxLabel = Label[v2]; if (minLabel > Label[v2]){ minLabel = Label[v2]; maxLabel = Label[v1]; } for (int i=0; i<nVer; i++) if (Label[i] == maxLabel){ Label[i] = minLabel; }}/* LƯU Ý: Ghi nhận đoạn mã sai sau đây đế rút kinh nghiệm:if (Label[v1] < Label[v2]){ for (int i=0; i<nVer; i++) if (Label[i] == Label[v2]) Label[i] = Label[v1];}else{ for (int i=0; i<nVer; i++) if (Label[i] == Label[v1]) Label[i] = Label[v2];}*/
4. 4. void KruskalAlgo::InitAlg(){ Label.resize(nVer); for (int i=0; i<Label.size(); i++){ Label[i]=i; } sort(Edges.begin(), Edges.end());}int KruskalAlgo::RunAlg(){ // Thuaät toaùn chính InitAlg(); // Böôùc 1 int nE = Edges.size(), nT = 0; for (int i=0; i<nE; i++) { // Böôùc 2 Edge e=Edges[i]; int v1=e.getV1(), v2=e.getV2(); if (Label[v1] != Label[v2]){ T.push_back(e); UpdateLabels(v1, v2); } if ( (nT=T.size()) == nVer-1) break; } return nT==nVer-1;}void KruskalAlgo::ShowT(ostream& outDev){ int nT = T.size(); float w=0; for (int i=0; i<nT; i++){ outDev << T[i] << endl; w += T[i].getW(); } outDev << "Total weight = " << w << endl;}// end of File Kruskal.cpp---------------------------
5. 5. // File MainPrg.cpp---------------------------------------#include "Kruskal.h"#include <conio.h>void main() // Lấy dữ liệu từ file{ KruskalAlgo g; if (g.LoadEdges("gData.txt")){ g.RunAlg(); g.ShowT(cout); } else cout << "File not found!" << endl; getch();}/*void main() // Lấy dữ liệu từ thiết bị nhập chuẩn (bàn phím console hay tập tin){ KruskalAlgo g; g.LoadEdges(cin); g.RunAlg(); g.ShowT(cout); getch();}*/// end of File MainPrg.cpp-------------------------------------------