my_solutions/NOIP/2003/Epidemic.cpp

//这个程序能得90分，其中第九组数据应该输出55，但这个程序输出56，不知道为什么。
#include <cstdio>
#include <cstring>
int n, p,maxd;
int w[400];
typedef struct Edge
{
    int from, to;
    Edge* next;
    Edge(int f, int t, Edge* n = 0) :from(f), to(t), next(n) {}
}*lpEdge;
#define addEdge(Gp, x, y) (Gp)[x] = new Edge((x), (y), (Gp)[x]);
lpEdge G1[302], G[302], Dep[302];
bool vis[302];
void build(int id)
{
    vis[id] = true;
    for (lpEdge cur = G1[id]; cur; cur = cur->next)
        if (!vis[cur->to])
        {
            addEdge(G, id, cur->to);
            build(cur->to);
        }
}
int getWeight(int id)
{
    if (~w[id]) return w[id];
    else
    {
        int cnt = 1;
        for (lpEdge cur = G[id]; cur; cur = cur->next)
            cnt += getWeight(cur->to);
        return w[id] = cnt;
    }
}
void getDepth(int id,int d)
{
    if(id>maxd) maxd=id;
    addEdge(Dep,d,id);
    for(lpEdge cur=G[id]; cur; cur=cur->next)
        getDepth(cur->to,d+1);
}
void setSafe(int id)
{
    vis[id]=true;
    for(lpEdge cur=G[id]; cur; cur=cur->next)
        setSafe(cur->to);
}
int main()
{
    memset(w, -1, sizeof(w));
    scanf("%d%d", &n, &p);
    for (int i = 0, a, b; i < p; i++)
    {
        scanf("%d%d", &a, &b);
        addEdge(G1, a, b);
        addEdge(G1, b, a);
    }
    build(1);
    getWeight(1);
    getDepth(1,0);
    memset(vis,0,sizeof(vis));
    int safeCnt=0;
    for(int i=1,maxn,maxid; i<=maxd; i++)
    {
        maxn=maxid=0;
        for(lpEdge cur=Dep[i]; cur; cur=cur->next)
            if(!vis[cur->to]&&w[cur->to]>maxn) maxn=w[maxid=cur->to];
        safeCnt+=maxn;
        setSafe(maxid);
    }
    printf("%d",n-safeCnt);
    return 0;
}