poj3256

bfs

#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cstring>
using namespace std;

#define maxc 105
#define maxn 1005
#define maxm 10005

struct Edge
{
    int v, next;
} edge[maxm];

int cow, n, m;
int head[maxn];
int ncount;
bool vis[maxn];
int reach[maxn];
int q[maxn];
int pos[maxc];

void addedge(int a, int b)
{
    edge[ncount].v = b;
    edge[ncount].next = head[a];
    head[a] = ncount++;
}

void input()
{
    scanf("%d%d%d", &cow, &n, &m);
    for (int i = 0; i < cow; i++)
    {
        scanf("%d", &pos[i]);
        pos[i]--;
    }
    for (int i = 0; i < m; i++)
    {
        int a, b;
        scanf("%d%d", &a, &b);
        addedge(a - 1, b - 1);
    }
}

void bfs(int s)
{
    int front = 0, rear = 0;

    q[rear++] = s;
    vis[s] = true;
    while (front != rear)
    {
        int u = q[front++];
        reach[u]++;
        for (int i = head[u]; ~i; i = edge[i].next)
        {
            int v = edge[i].v;
            if (vis[v])
                continue;
            q[rear++] = v;
            vis[v] = true;
        }
    }
}

int work()
{
    memset(reach, 0, sizeof(reach));
    for (int i = 0; i < cow; i++)
    {
        memset(vis, 0, sizeof(vis));
        bfs(pos[i]);
    }
    int ret = 0;
    for (int i = 0; i < n; i++)
        if (reach[i] == cow)
            ret++;
    return ret;
}

int main()
{
    //freopen("t.txt", "r", stdin);
    memset(head, -1, sizeof(head));
    ncount = 0;
    input();
    printf("%d\n", work());
    return 0;
}