用c语言以邻接表的形式创建一个无向图：分析过程

创建一个无向图，需要定义图的节点和边。邻接表是一种常见的图存储方式，其基本思想是将每个节点的邻居节点存储在一个链表中。

1. 定义节点结构体

首先，我们需要定义节点结构体。每个节点包含一个标识符和指向邻居节点的指针。

typedef struct node {
    int value;  // 节点的标识符
    struct node *next;  // 指向下一个邻居节点的指针
} Node;

2. 定义图结构体

然后，我们定义图结构体。图结构体包含一个节点数组和节点数量。

typedef struct graph {
    Node **nodes;  // 节点数组，每个节点指向一个邻居链表
    int numNodes;  // 节点数量
} Graph;

3. 初始化图

接着，我们初始化图。我们需要为节点数组分配内存，并将每个节点的邻居链表初始化为空。

Graph *createGraph(int numNodes) {
    Graph *graph = (Graph *)malloc(sizeof(Graph));
    graph->numNodes = numNodes;
    graph->nodes = (Node **)malloc(numNodes * sizeof(Node *));
    for (int i = 0; i < numNodes; i++) {
        graph->nodes[i] = NULL;
    }
    return graph;
}

4. 添加边

现在，我们可以添加边了。对于无向图，每条边需要在两个节点之间建立连接。我们可以通过向节点的邻居链表中添加节点来实现连接。

void addEdge(Graph *graph, int src, int dest) {
    // 添加从 src 到 dest 的边
    Node *node = (Node *)malloc(sizeof(Node));
    node->value = dest;
    node->next = graph->nodes[src];
    graph->nodes[src] = node;

    // 添加从 dest 到 src 的边
    node = (Node *)malloc(sizeof(Node));
    node->value = src;
    node->next = graph->nodes[dest];
    graph->nodes[dest] = node;
}

5. 打印图

最后，我们可以打印图，以验证我们的实现是否正确。

void printGraph(Graph *graph) {
    for (int i = 0; i < graph->numNodes; i++) {
        printf("Node %d: ", i);
        Node *node = graph->nodes[i];
        while (node) {
            printf("%d ", node->value);
            node = node->next;
        }
        printf("\n");
    }
}

完整代码如下：

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

typedef struct node {
    int value;
    struct node *next;
} Node;

typedef struct graph {
    Node **nodes;
    int numNodes;
} Graph;

Graph *createGraph(int numNodes) {
    Graph *graph = (Graph *)malloc(sizeof(Graph));
    graph->numNodes = numNodes;
    graph->nodes = (Node **)malloc(numNodes * sizeof(Node *));
    for (int i = 0; i < numNodes; i++) {
        graph->nodes[i] = NULL;
    }
    return graph;
}

void addEdge(Graph *graph, int src, int dest) {
    Node *node = (Node *)malloc(sizeof(Node));
    node->value = dest;
    node->next = graph->nodes[src];
    graph->nodes[src] = node;

    node = (Node *)malloc(sizeof(Node));
    node->value = src;
    node->next = graph->nodes[dest];
    graph->nodes[dest] = node;
}

void printGraph(Graph *graph) {
    for (int i = 0; i < graph->numNodes; i++) {
        printf("Node %d: ", i);
        Node *node = graph->nodes[i];
        while (node) {
            printf("%d ", node->value);
            node = node->next;
        }
        printf("\n");
    }
}

int main() {
    int numNodes = 5;
    Graph *graph = createGraph(numNodes);
    addEdge(graph, 0, 1);
    addEdge(graph, 0, 2);
    addEdge(graph, 1, 3);
    addEdge(graph, 2, 3);
    addEdge(graph, 2, 4);
    printGraph(graph);
    return 0;
}