PAT甲级A1076---图的遍历

1076 Forwards on Weibo (30分)

分析：

C++：

#include <cstdio>
#include <vector>
#include <queue>
#include <cstring>

using namespace std;

const int maxn = 1010;
struct Node {
    int id;
    int layer;
};
vector<Node> G[maxn];
bool inq[maxn];
int n, l;

int bfs(int index) {
    int forwardNum = 0;
    queue<Node> q;
    Node start;
    start.id = index;
    start.layer = 0;
    q.push(start);
    inq[start.id] = true;
    while (!q.empty()) {
        Node frontNode = q.front();
        q.pop();
        int front = frontNode.id;
        for (int i = 0; i < G[front].size(); i++) {
            Node nextNode = G[front][i];
            nextNode.layer = frontNode.layer + 1;
            if (inq[nextNode.id] == false && nextNode.layer <= l) {
                q.push(nextNode);
                inq[nextNode.id] = true;
                forwardNum++;
            }
        }
    }
    return forwardNum;
}

int main() {
    Node user;
    scanf("%d%d", &n, &l);
    int followNum, followId;
    for (int i = 1; i <= n; i++) {
        user.id = i;
        scanf("%d", &followNum);
        for (int j = 0; j < followNum; j++) {
            scanf("%d", &followId);
            G[followId].push_back(user);
        }
    }
    int queryNum, s;
    scanf("%d", &queryNum);
    for (int i = 0; i < queryNum; i++) {
        memset(inq, false, sizeof(inq));
        scanf("%d", &s);
        int forwardNum = bfs(s);
        printf("%d\n", forwardNum);
    }
    return 0;
}