图的存储和遍历C++实现

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最近在做一些OJ题目时,感觉自己图的应用还不够熟练。所以又翻书看别人的博客复习了一下,现把图的常用内容总结如下:

图的常用存储方法有:邻接矩阵和邻接表

遍历方法有:按深度遍历(DFS),按广度遍历(BFS)

下面的代码都是C++写的,用了一些STL库的容器:

邻接矩阵:

#include <stdio.h>
#include <stdlib.h>
 
typedefstructGraph
{
    char vexs[100];            //顶点表
    int   arc[100][100];         //邻接矩阵,可看作边
    intnumVertexes, numEdges;      //图中当前的顶点数和边数
}g;
 
//定位
intlocates(Graph *g, charch)
{
    inti = 0;
    for(i = 0; i < g->numVertexes; i++)
    {
        if(g->vexs[i] == ch)
        {
            break;
        }
    }
    if(i >= g->numVertexes)
    {
        return-1;
    }
     
    returni;
}
 
//建立一个无向网图的邻接矩阵表示
voidCreateGraph(Graph *g)
{
    inti, j, k, w;
    printf("输入顶点数和边数:\n");
    scanf("%d,%d", &(g->numVertexes), &(g->numEdges));
 
    for(i = 0; i < g->numVertexes; i++)
    {
        g->vexs[i] = getchar();
        while(g->vexs[i] == '\n')
        {
            g->vexs[i] = getchar();
        }
    }
     
    for(i = 0; i < g->numEdges; i++)
    {
        for(j = 0; j < g->numEdges; j++)
        {
            g->arc[i][j] = INFINITY; //邻接矩阵初始化
        }
    }
    for(k = 0; k < g->numEdges; k++)
    {
        charp, q;
        printf("输入边(vi,vj)上的下标i,下标j和权值:\n");
         
        p = getchar();
        while(p == '\n')
        {
            p = getchar();
        }
        q = getchar();
        while(q == '\n')
        {
            q = getchar();
        }
        scanf("%d", &w);   
         
        intm = -1;
        intn = -1;
        m = locates(g, p);
        n = locates(g, q);
        if(n == -1 || m == -1)
        {
            fprintf(stderr,"there is no this vertex.\n");
            return;
        }
        //getchar();
        g->arc[m][n] = w;
        g->arc[n][m] = g->arc[m][n];  //因为是无向图,矩阵对称
    }
}
 
//打印图
voidprintGraph(Graph g)
{
    inti, j;
    for(i = 0; i < g.numVertexes; i++)
    {
        for(j = 0; j < g.numVertexes; j++)
        {
            printf("%d  ", g.arc[i][j]);
        }
        printf("\n");
    }
}
 
intmain(intargc,char**argv)
{
    Graph g;
     
    //邻接矩阵创建图
    CreateGraph(&g);
    printGraph(g);
    return0;
}


基于邻接矩阵的深度优先遍历(DFS)(类似二叉树的前序遍历)(用递归)
#define MAXVEX  100     //最大顶点数
int visited[MAXVEX];        //访问标志数组
#define TRUE 1
#define FALSE 0
//邻接矩阵的深度优先递归算法
voidDFS(Graph g, inti)
{
    intj;
    visited[i] = TRUE;
    printf("%c ", g.vexs[i]);                           //打印顶点,也可以其他操作
    for(j = 0; j < g.numVertexes; j++)
    {
        if(g.arc[i][j] == 1 && !visited[j])
        {
            DFS(g, j);                  //对为访问的邻接顶点递归调用
        }
    }
}
 
//邻接矩阵的深度遍历操作
voidDFSTraverse(Graph g)
{
    inti;
    for(i = 0; i < g.numVertexes; i++)
    {
        visited[i] = FALSE;         //初始化所有顶点状态都是未访问过状态
    }
    for(i = 0; i < g.numVertexes; i++)
    {
        if(!visited[i])            //对未访问的顶点调用DFS,若是连通图,只会执行一次
        {
            DFS(g,i);
        }
    }
}


基于邻接矩阵的广度优先遍历(BFS)(类似二叉树的层次遍历)(不用递归):

//邻接矩阵的广度遍历算法
#include<queue>
voidBFSTraverse(Graph g)
{
    inti, j;
    queue<int> q;
    for(i = 0; i < g.numVertexes; i++)
    {
        visited[i] = FALSE;
    }

    for(i = 0; i < g.numVertexes; i++)//对每个顶点做循环
    {
        if(!visited[i])              //若是未访问过
        {
            visited[i] = TRUE;
            printf("%c ", g.vexs[i]); //打印结点,也可以其他操作
            q.push(i);          //将此结点入队列
            while(!q.empty())    //将队中元素出队列,赋值给
            {
                intm;
                m=q.front();
q.pop();       
                for(j = 0; j < g.numVertexes; j++)
                {
                    //判断其他顶点若与当前顶点存在边且未访问过
                    if(g.arc[m][j] == 1 && !visited[j])
                    {
                        visited[j] = TRUE;
                        printf("%c ", g.vexs[j]);
                        q.push(j);
                    }
                }
            }
        }
    }
}


邻接表结构:

#include <stdio.h>
#include<stdlib.h>
#define MAXVEX 1000         //最大顶点数
 
typedefstructEdgeNode        //边表结点
{
    intadjvex;        //邻接点域,存储该顶点对应的下标
    int weigth;        //用于存储权值,对于非网图可以不需要
    structEdgeNode *next;      //链域,指向下一个邻接点
}EdgeNode;
 
typedefstructVertexNode      //顶点表结构
{
    char data;        //顶点域,存储顶点信息
    EdgeNode *firstedge;        //边表头指针
}VertexNode, AdjList[MAXVEX];
 
typedefstruct
{
    AdjList adjList;
    intnumVertexes, numEdges;  //图中当前顶点数和边数
}GraphList;
 
intLocate(GraphList *g, charch)
{
    inti;
    for(i = 0; i < MAXVEX; i++)
    {
        if(ch == g->adjList[i].data)
        {
            break;
        }
    }
    if(i >= MAXVEX)
    {
        fprintf(stderr,"there is no vertex.\n");
        return-1;
    }
    returni;
}
 
//建立图的邻接表结构
voidCreateGraph(GraphList *g)
{
    inti, j, k;
    EdgeNode *e;
    EdgeNode *f;
    printf("输入顶点数和边数:\n");
    scanf("%d,%d", &g->numVertexes, &g->numEdges);
     //建立顶点表
    for(i = 0; i < g->numVertexes; i++)
    {
        printf("请输入顶点%d:\n", i);
        g->adjList[i].data = getchar();         //输入顶点信息
        g->adjList[i].firstedge = NULL;          //将边表置为空表
        while(g->adjList[i].data == '\n')
        {
            g->adjList[i].data = getchar();
        }
    }
    //建立边表
    for(k = 0; k < g->numEdges; k++)
    {
        printf("输入边(vi,vj)上的顶点序号:\n");
        charp, q;
        p = getchar();
        q = getchar();
        intm, n;
        m = Locate(g, p);
        n = Locate(g, q);
     
        e = (EdgeNode *)malloc(sizeof(EdgeNode));//向内存申请空间,生成边表结点
        e->adjvex = n; 
        e->next = g->adjList[m].firstedge;//将e指针指向当前顶点指向的结构
        g->adjList[m].firstedge = e;//将当前顶点的指针指向e
        
f = (EdgeNode *)malloc(sizeof(EdgeNode));
        f->adjvex = m;
        f->next = g->adjList[n].firstedge;
        g->adjList[n].firstedge = f;
    }
}

voidprintGraph(GraphList *g)
{
    inti = 0; 
    while(g->adjList[i].firstedge != NULL && i < MAXVEX)
    {
        printf("顶点:%c  ", g->adjList[i].data);
        EdgeNode *e = NULL;
        e = g->adjList[i].firstedge;
        while(e != NULL)
        {
            printf("%d  ", e->adjvex);
            e = e->next;
        }
        i++;
        printf("\n");
    }
}
 
intmain(intargc,char**argv)
{
    GraphList g;
    CreateGraph(&g);
    printGraph(&g);
    return0;
}
基于邻接表存储结构的深度优先遍历
//邻接表的深度递归算法
void DFS(GraphList g,int i)
{
EdgeNode *p;
visit[i] = 1;
printf("%c",g->adjList[i].data);
p = g->adjList[i].firstedge;
while(p)
{
if(!visited[p->adjvex])
{
DFS(g,p->adjvex);
}
p = p->next;
}
}

//邻接表的深度遍历操作
void DFSTraverse(GraphList g)
{

int i;

for(i=0;i<g.numVertexes;i++)

{

visited[i] = 0;

}

for(i=0;i<g.numVertexes;i++)

{

if(!visited[i])

{

DFS(g,i);

}

}

}

对比两个不同的存储结构的深度优先遍历算法,对于n个顶点e条边的图来说,邻接矩阵由于是二维数组,要查找某个顶点的邻接点需要访问矩阵中的所有元素,因为需要O(n2)的时间。而邻接表做存储结构时,找邻接点所需的时间取决于顶点和边的数量,所以是O(n+e)。显然对于点多边少的稀疏图来说,邻接表结构使得算法在时间效率上大大提高。


基于邻接表的广度优先遍历:


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//邻接表的广度遍历算法
#include<queue>
voidBFSTraverse(GraphList g)
{
    inti;
    EdgeNode *p;
    queue q;
    for(i = 0; i < g.numVertexes; i++)
    {
        visited[i] = 0;
    }
    for(i = 0; i < g.numVertexes; i++)
    {
        if(!visited[i])
        {
            visited[i] = 1;
            printf("%c ", g.adjList[i].data);   //打印顶点,也可以其他操作
            q.push(i);
            while(!q.empty())
            {
                intm;
m = q.front();
q.pop();
                p = g.adjList[m].firstedge;     找到当前顶点边表链表头指针
                while(p)
                {
                    if(!visited[p->adjvex])
                    {
                        visited[p->adjvex] = 1;
                        printf("%c ", g.adjList[p->adjvex].data);
                        q.push(p->adjvex);
                    }
                    p = p->next;
                }
            }
        }
    }
}

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