题目：

题解：

struct Node** visited;
int* state;  //数组存放结点状态 0：结点未创建 1：仅创建结点 2：结点已创建并已填入所有内容

void bfs(struct Node* s) {
    if (visited[s->val] && state[s->val] == 2) {
        return;
    }
    struct Node* neighbor;
    if (visited[s->val]) {
        neighbor = visited[s->val];
        neighbor->val = s->val;
        neighbor->numNeighbors = s->numNeighbors;
        neighbor->neighbors = (struct Node**)malloc(sizeof(struct Node*) * neighbor->numNeighbors);
    } else {
        // 如果没有被访问过，就克隆并存储在哈希表中
        neighbor = (struct Node*)malloc(sizeof(struct Node));
        neighbor->val = s->val;
        neighbor->numNeighbors = s->numNeighbors;
        neighbor->neighbors = (struct Node**)malloc(sizeof(struct Node*) * neighbor->numNeighbors);
        visited[s->val] = neighbor;
    }
    for (int i = 0; i < neighbor->numNeighbors; i++) {
        if (visited[s->neighbors[i]->val]) {
            neighbor->neighbors[i] = visited[s->neighbors[i]->val];
        } else {
            visited[s->neighbors[i]->val] = (struct Node*)malloc(sizeof(struct Node));
            state[s->neighbors[i]->val] = 1;
            neighbor->neighbors[i] = visited[s->neighbors[i]->val];
        }
    }
    state[neighbor->val] = 2;
}

struct Node* cloneGraph(struct Node* s) {
    if (s == NULL) {
        return NULL;
    }

    // 将题目给定的节点添加到队列
    struct Node *QUEUE[101], *p;
    int head = -1, eneighbor = -1, i, flag[101];

    visited = (struct Node**)malloc(sizeof(struct Node*) * 101);
    memset(visited, 0, sizeof(struct Node*) * 101);
    state = (int*)malloc(sizeof(int) * 101);
    memset(state, 0, sizeof(int) * 101);
    memset(flag, 0, sizeof(int) * 101);

    // 克隆第一个节点并存储到哈希表中
    QUEUE[++eneighbor] = s;

    // 广度优先搜索
    while (head != eneighbor) {
        // 取出队列的头节点
        p = QUEUE[++head];
        // 遍历该节点的邻居
        bfs(p);
        for (i = 0; i < p->numNeighbors; i++) {
            if (!flag[p->neighbors[i]->val]) {
                // 将邻居节点加入队列中
                QUEUE[++eneighbor] = p->neighbors[i];
                flag[p->neighbors[i]->val] = 1;
            }
        }
    }

    return visited[s->val];
}