[DSA] Figure-adjacency list implementation diagram (3)

The meaning of the adjacency list has already been said in the previous blog post ( basics of graph theory ).
This chapter will use the adjacency list to create a graph, and give the code implementation.
In order to make it easier to see the implementation of the code, I will directly copy the graph in the foundation of graph theory.

Diagram of adjacency list

Code

See github for the code of all data structure algorithms , and the code address of this article .

/*
* @Author: jobbofhe
* @Date:   2019-11-01 16:44:27
* @Last Modified by:   Administrator
* @Last Modified time: 2019-11-05 09:45:09
*/

#include <stdio.h>
#include <stdlib.h>
#include <malloc.h>
#include <string.h>

#define  IS_LETTER(c)   ( (((c) >= 'a') && ((c) <= 'z')) || (((c) >= 'A') && ((c) <= 'Z')) )
#define  LENGTH(c)      (sizeof(c)/(sizeof(c[0])))

#define MAX_VERTEX (200)

// 邻接表链表中的节点
typedef struct Node_
{
    int index_vex;
    struct Node_ *next_edge;

}Node, *pNode;

// graph 顶点信息
typedef struct VertexNode_
{
    char data;
    Node *first_edge;

}VertexNode;

// 邻接表结构体
typedef struct ListListGraph_
{
    int vertex_number;
    int edge_number;
    VertexNode vertex[MAX_VERTEX];

}ListGraph;

int get_position(ListGraph list_graph, char ch)
{
    for (int i = 0; i < list_graph.vertex_number; ++i)
    {
        if (list_graph.vertex[i].data == ch)
        {
            return i;
        }
    }

    return -1;
}

void append_tail(Node *list, Node *node)
{
    Node *p = list;

    while(p->next_edge) 
    {
        p = p->next_edge;
    }
    p->next_edge = node;
}

/*
 * 创建图(用已提供的矩阵)
 */
ListGraph* create_graph(char *vertex, char edges[][2], int vlen, int elen)
{
    int i, p1, p2;
    Node *node1, *node2;
    ListGraph* pG;
    
    if ((pG=(ListGraph*)malloc(sizeof(ListGraph))) == NULL )
    {
        return NULL;
    }
    memset(pG, 0, sizeof(ListGraph));

    // 初始化"顶点数"和"边数"
    pG->vertex_number = vlen;
    pG->edge_number = elen;
    printf("顶点数量： %d  边数 :%d\n", vlen, elen);
    // 初始化"顶点"
    for (i = 0; i < pG->vertex_number; i++)
    {
        pG->vertex[i].data = vertex[i];
        pG->vertex[i].first_edge = NULL;
    }

    // 初始化"边"
    for (i = 0; i < pG->edge_number; i++)
    {
        // 读取边的起始顶点和结束顶点
        p1 = get_position(*pG, edges[i][0]);
        p2 = get_position(*pG, edges[i][1]);

        // A-->B
        node1 = (Node *)malloc(sizeof(Node));
        node1->index_vex = p2;
        // 将node1, 插在链表末尾
        if (pG->vertex[p1].first_edge == NULL)
        {
            pG->vertex[p1].first_edge = node1;
        }
        else
        {
            append_tail(pG->vertex[p1].first_edge, node1);
        }

        // B-->A
        node2 = (Node *)malloc(sizeof(Node));
        node2->index_vex = p1;
        if (pG->vertex[p2].first_edge == NULL)
        {
            pG->vertex[p2].first_edge = node2;
        }
        else
        {
            append_tail(pG->vertex[p2].first_edge, node2);
        }
    }

    return pG;
}

void print_graph(ListGraph graph)
{
    printf("顶点数量： %d\n", graph.vertex_number);


    for (int i = 0; i < graph.vertex_number; ++i)
    {
        printf("[%d](%c)", i, graph.vertex[i].data);
        Node *node = graph.vertex[i].first_edge;
        while(node != NULL) 
        {
            printf("-->[%d](%c)", node->index_vex, graph.vertex[node->index_vex].data);
            node = node->next_edge;
        }

        printf("\n");
    }
}

int main(int argc, char const *argv[])
{
    char vertex[] = {'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H'};
    char edges[][2] = {
        {'A', 'C'}, 
        {'A', 'D'}, 
        {'A', 'F'}, 
        {'B', 'C'}, 
        {'C', 'D'}, 
        {'F', 'G'},
        {'G', 'E'},
        {'E', 'H'}}; 

    ListGraph* p_graph_2 = create_graph(vertex, edges, LENGTH(vertex), LENGTH(edges));
    print_graph(*p_graph_2);
    return 0;
}

Results verification

Generalized to directed graph

Unlike the undirected graph, the direction of the edge of the directed graph is unidirectional. You only need to modify one place in the code.

# 修改接口
create_graph(char *vertex, char edges[][2], int vlen, int elen)

# 删除掉其中以下行即可
 // B-->A
node2 = (Node *)malloc(sizeof(Node));
node2->index_vex = p1;
if (pG->vertex[p2].first_edge == NULL)
{
    pG->vertex[p2].first_edge = node2;
}
else
{
    append_tail(pG->vertex[p2].first_edge, node2);
}