利用深度遍历算法实现

int getNum(MGraph G) {
    int i, count = 0;
    for(i = 0; i < G.vexnum; i++) 
        visited[i] = false;
    for(i = 0; i < G.vexnum; i++)
        if(!visited[i]) {
            count++;
            DFS(G, i);
        }
    return count;
}

测试代码如下：

以下代码以邻接表作为图的存储方式

#include <stdio.h>
#include <stdlib.h>
#define MAXVEX 10
typedef int VertexType;
typedef struct arcNode {  
    int adjvex;
    struct arcNode *next;
} arcNode;
typedef struct vertexNode { 
    VertexType data;
    arcNode *first;
} vertexNode, adjList[MAXVEX];
typedef struct { 
    adjList adjlist;
    int vexnum, arcnum;
} ALGraph;
//邻接表初始化 
void createALGraph(ALGraph &G) { 
    int i, j, k;
    arcNode *e;
    printf("输入顶点数和边数：\n");
    scanf("%d%d", &G.vexnum, &G.arcnum); 
    for(i = 0; i < G.vexnum; i++) {
        scanf("%d", &G.adjlist[i].data); 
        G.adjlist[i].first = NULL;
    }
    for(k = 0; k < G.arcnum; k++) {
        printf("输入边(vi, vj)上的顶点序号：\n");
        scanf("%d%d", &i, &j); 
        e = (arcNode *)malloc(sizeof(arcNode)); 
        e->adjvex = i;
        e->next = G.adjlist[j].first;
        G.adjlist[j].first = e;
        
        e = (arcNode *)malloc(sizeof(arcNode));
        e->adjvex = j;
        e->next = G.adjlist[i].first;
        G.adjlist[i].first = e;
    }
}
//深度优先遍历
int visited[MAXVEX];
void DFS(ALGraph G, int i) {
    arcNode *p;
    visited[i] = 1;
    p = G.adjlist[i].first;
    while(p) {
        if(!visited[p->adjvex])
            DFS(G, p->adjvex);
        p = p->next;
    }
}
//求连通分量 
int getNum(ALGraph G) {
    int i, count = 0; //记录连通分量个数 
    for(i = 0; i < G.vexnum; i++) 
        visited[i] = 0;
    for(i = 0; i < G.vexnum; i++)
        if(!visited[i]) {
            count++;
            DFS(G, i);
        }  
    return count;      
}
int main() {
    ALGraph G;
    createALGraph(G);
    printf("%d", getNum(G));
    return 0;
}