图的邻接表结构图：
代码部分：
adj_list_graph.h

#ifndef _ADJ_LIST_GRAPH_H
#define _ADJ_LIST_GRAPH_H
#include <stdio.h>
#include <stdlib.h>
#define GRAPH_NODE_INF (-1)
#define GRAPH_ERR (-1)
#define GRAPH_SUCCESS 0

typedef char VertexType;
typedef struct _edge_node {
    VertexType data;
    int weight;
    struct _edge_node *next;
}EdgeNode, *PEdgeNode;

typedef struct _vertex_node {
    VertexType data;
    PEdgeNode head;
}VertexNode, *PVertexNode;

typedef struct _adj_graph {
    PVertexNode node;
    int edgeSize;
    int nodeSize;
}AdjGraph, *PAdjGraph;

/* 初始化一个无向图 */
PAdjGraph GraphInit();

#endif

adj_list_graph.c

#include "adj_list_graph.h"

PAdjGraph GraphInit()
{
    PAdjGraph graph = (PAdjGraph)malloc(sizeof(AdjGraph));
    if(graph == NULL) {
        perror("graph malloc error.");
        return (PAdjGraph)GRAPH_ERR;
    }
    printf("Please input the number of vertex nodes.\n");
    scanf("%d", &graph->nodeSize);
    printf("Please input the number of edges.\n");
    scanf("%d", &graph->edgeSize);
    graph->node = (PVertexNode)malloc(sizeof(VertexNode) * graph->nodeSize);
    if(graph->node == NULL) {
        perror("vertex node malloc error.");
        return (PAdjGraph)GRAPH_ERR;
    }
    /* get the node info of graph */
    for(int i=0; i<graph->nodeSize; i++) {
        printf("Please input the info of Vertex node[%d].\n", i+1);
        scanf("%c\n", &graph->node[i].data);
        graph->node[i].head = NULL;
    }
    char ch;
    while((ch=getchar()) != '\n');
    int iValue, jValue, weight;
    for(int i=0; i<graph->edgeSize; i++) {
        printf("please input the edge[%d] by (i,j)\n", i+1);
        scanf("%d,%d", &iValue, &jValue);
        printf("i=%d,j=%d\n", iValue, jValue);
        printf("Please input the weight of edge[%d].\n", i+1);
        scanf("%d", &weight);
        if(iValue<0 || iValue>=graph->nodeSize || jValue<0 || jValue>=graph->edgeSize || weight <= 0) {
            perror("node info error.");
            return (PAdjGraph)GRAPH_ERR;
        }
        PEdgeNode addNodeI = (PEdgeNode)malloc(sizeof(EdgeNode));
        if(addNodeI == NULL) {
            perror("addNodeI malloc error.");
            return(PAdjGraph)GRAPH_ERR;
        }
        addNodeI->data = graph->node[iValue].data;
        addNodeI->weight = weight;
        addNodeI->next = graph->node[iValue].head;
        graph->node[iValue].head = addNodeI;

        PEdgeNode addNodeJ = (PEdgeNode)malloc(sizeof(EdgeNode));
        if(addNodeJ == NULL) {
            perror("addNodeJ malloc error.");
            return (PAdjGraph)GRAPH_ERR;
        }
        addNodeJ->data = graph->node[jValue].data;
        addNodeJ->weight = weight;
        addNodeJ->next = graph->node[jValue].head;
        graph->node[jValue].head = addNodeJ;
    }
    printf("graph init completed.\n");
    return graph;
}

main.c

#include "adj_list_graph.c"

int main(void)
{
    PAdjGraph myGraph = GraphInit();
    return 0;
}