求最小生成树——Kruskal算法

#include <iostream>
#include <cstring>
#define MaxSize 20
using namespace std;

struct Edge{
    int begin;     
    int end;     
    int weight;  
}; 
struct Graph{
    char ver[MaxSize + 1];
    int edg[MaxSize][MaxSize];
};

void CreateGraph(Graph *g) {
    int VertexNum;
    char Ver;
    int i = 0;
    cout << "输入图的顶点:" << endl;
    while ((Ver = getchar()) != ‘\n‘) {
        g->ver[i] = Ver;
        i++;
    }
    g->ver[i] = ‘\0‘;
    VertexNum = strlen(g->ver);
    cout << "输入相应的邻接矩阵" << endl;
    for (int i = 0; i < VertexNum; i++) {
        for (int j = 0; j < VertexNum; j++) {
            cin >> g->edg[i][j];    //输入0则为没有边相连啊
        }
    }
}

void PrintGraph(Graph g) {
    int VertexNum = strlen(g.ver);
    cout << "图的顶点为:" << endl;
    for (int i = 0; i < VertexNum; i++) {
        cout << g.ver[i] << " ";
    }
    cout << endl;
    cout << "图的邻接矩阵为:" << endl;
    for (int i = 0; i < VertexNum; i++) {
        for (int j = 0; j < VertexNum; j++) {
            cout << g.edg[i][j] << " ";
        }
        cout << endl;
    }
}

int getVerNum(Graph g) {
    return strlen(g.ver);
}

int getEdgeNum(Graph g) {
    int res = 0;
    int VertexNum = getVerNum(g);
    for (int i = 0; i < VertexNum; i++) {
        //邻接矩阵对称，计算上三角元素和即可
        for (int j = i + 1 /*假设没有自己指向自己的*/; j < VertexNum; j++) {
            if (g.edg[i][j] != 0) res++;
        }
    }    
    return res;
}

Edge *CreateEdges(Graph g) {
    int k = 0;
    int EdgeNum = getEdgeNum(g);
    int VertexNum = getVerNum(g);
    Edge * p = new Edge[EdgeNum];
    for (int i = 0; i < VertexNum; i++) {
        for (int j = i; j < VertexNum; j++) {
            if (g.edg[i][j] != 0) {
                p[k].begin = i;
                p[k].end = j;
                p[k].weight = g.edg[i][j];
                k++;
            }
        }
    }
    for (int i = 0; i < EdgeNum - 1; i++) {
        Edge minWeightEdge = p[i];
        for (int j = i + 1; j < EdgeNum; j++) {
            if (minWeightEdge.weight > p[j].weight) {
                Edge temp = minWeightEdge;
                minWeightEdge = p[j];
                p[j] = temp;
            }
        }
        p[i] = minWeightEdge;
    }
    return p;
}

void Kruskal(Graph g) {
    int VertexNum = getVerNum(g);
    int EdgeNum = getEdgeNum(g);
    Edge *p = CreateEdges(g);
    int *index = new int[VertexNum];    //index数组，其元素为连通分量的编号，index[i]==index[j]表示编号为i和j的顶点在同一连通分量中
    int *MSTEdge = new int[VertexNum - 1];    //用来存储已确定的最小生成树的**边的编号**，共VertexNum-1条边
    int k = 0;
    int WeightSum = 0;
    int IndexBegin, IndexEnd;
    for (int i = 0; i < VertexNum; i++) {
        index[i] = -1;    //初始化所有index为-1
    }
    for (int i = 0; i < VertexNum - 1; i++) {
        for (int j = 0; j < EdgeNum; j++) {
            if ( !(index[p[j].begin] >= 0 && index[p[j].end] >= 0 && index[p[j].begin] == index[p[j].end] /*若成立表明p[j].begin和p[j].end已在同一连通块中（且可相互到达，废话）*/) ) {
                MSTEdge[i] = j;
                if (index[p[j].begin] == -1 && index[p[j].end] == -1) {
                    index[p[j].begin] = index[p[j].end] = i;
                }
                else if (index[p[j].begin] == -1 && index[p[j].end] >= 0) {
                    index[p[j].begin] = i;
                    IndexEnd = index[p[j].end];
                    for (int n = 0; n < VertexNum; n++) {
                        if (index[n] == IndexEnd) {
                            index[n] == i;
                        }
                    }
                }
                else if (index[p[j].begin] >= 0 && index[p[j].end] == -1) {
                    index[p[j].end] = i;
                    IndexBegin = index[p[j].begin];
                    /*将连通分量合并（或者说将没加入连通分量的顶点加进去，然后将原来连通分量的值改了）*/
                    for (int n = 0; n < VertexNum; n++) {
                        if (index[n] == IndexBegin) {
                            index[n] == i;
                        }
                    }
                }
                else {
                    IndexBegin = index[p[j].begin];
                    IndexEnd = index[p[j].end];
                    for (int n = 0; n < VertexNum; n++) {
                        if (index[n] == IndexBegin || index[n] == IndexEnd) {
                            index[n] = i;
                         }
                    }
                }
                break;
            }
        }
    }
    cout << "MST的边为:" << endl;
    for (int i = 0; i < VertexNum - 1; i++) {
        cout << g.ver[p[MSTEdge[i]].begin] << "--" << g.ver[p[MSTEdge[i]].end] << endl;
        WeightSum += p[MSTEdge[i]].weight;
    }
    cout << "MST的权值为:" << WeightSum << endl;
}