POJ 3710 Christmas Game

POJ 3710 Christmas Game

图的删边游戏：

由于这个图比较特殊，我们推出如果环是奇环，则相当于加一条边，偶数环就相当于删除环，变成一个点。

不会缩环的默默YY了一个多小时才勉强搞定。

#include<iostream>#include<cstdio>#include<cstring>#include<cmath>#include<algorithm>#include<vector>#include<set>#include<queue>#include<map>using namespace std;#define FOR(i,a,b) for(int (i)=(a);(i)<=(b);(i)++)#define DOR(i,a,b) for(int (i)=(a);(i)>=(b);(i)--)#define CLR(a) memset((a),0,sizeof((a)))#define pb push_back#define mp make_pair#define ins insert#define F first#define S second#define bug puts("Oh Here!");#define nMax 2001#define oo 0x7fffffff#define eps 1e-8#define LL long long#define Vec vector<int>#define Pai pair<int,int>class tree{public:    int first[nMax],to[nMax],nxt[nMax],e,sg[nMax],vis[nMax],in[nMax];    int dfn[nMax],low[nMax],olen;    int adj[510][510];    int n,root;    void clear(){memset(first,-1,sizeof(first));e=0;CLR(adj);}    void addadge(int ,int );    void rebuild();    void dfs(int ,int ,int );    int dfs(int );    int sovle();};void tree::addadge(int u,int v){    to[e]=v;nxt[e]=first[u];first[u]=e;e++;    to[e]=u;nxt[e]=first[v];first[v]=e;e++;}int tree::dfs(int u){    sg[u]=0;    vis[u]=1;    for(int i=first[u];i!=-1;i=nxt[i])if(!in[to[i]] && !vis[to[i]]){        sg[u] ^= (dfs(to[i])+1);    }    return sg[u];}void tree::dfs(int u,int fa,int dep){    //printf("%d ->\n",u);    dfn[u]=low[u]=dep;    vis[u]=1;    for(int i=first[u],v;i!=-1;i=nxt[i]){        v=to[i];        if(vis[v]==1 && v!=fa){            olen = dfn[v]-dfn[u]+1;            low[u]=min(low[u],dfn[v]);        }        if(vis[v]==1 && v==fa && adj[u][v]>1){            olen = 2;            low[u]=min(low[u],dfn[v]);        }        if(!vis[v]){            dfs(v,u,dep+1);            low[u]=min(low[u],low[v]);        }    }    if(low[u]<dfn[u]){        in[u]=1;    }    if(low[u]==dfn[u]){        if(olen&1){           addadge(u,++n);           olen=0;        }    }    vis[u]=2;    //printf("<-\n");}void tree::rebuild(){    CLR(in);    CLR(vis);    olen=0;    dfs(root,-1,0);}int  tree::sovle(){    int m;    scanf("%d%d",&n,&m);    clear();    root=1;    for(int i=0,u,v;i<m;i++){        scanf("%d%d",&u,&v);        if(adj[u][v]==0)            addadge(u,v);        adj[u][v]++;        adj[v][u]++;    }    rebuild();    //FOR(i,1,n) printf("%d %d\n",i,in[i]);    CLR(vis);    dfs(root);    //printf("--%d\n",sg[root]);    return sg[root];}tree p;int main(){#ifndef ONLINE_JUDGE    freopen("input.txt","r",stdin);#endif    int t;    while(~scanf("%d",&t)){        int sg=0;        while(t--)            sg ^= p.sovle();        printf("%s\n",sg?"Sally":"Harry");    }    return 0;}