1A~这两天做题这么顺搞得我都不想去复习生态学了==

感觉这个题要比前一个简单一点,建边的时候如果有交叉就必须是一真一假。就是判断相交有点麻烦,开始想写函数判断两个线相交来着,发现还是判断不相交省事一点==

/***********
poj3207
2016.1.12
1172K	110MS	C++	1960B
***********/
#include <iostream>
#include<cstring>
#include<cstdio>
#include<vector>
using namespace std;
#define maxn 1000
struct TWOSAT
{
    int n;
    vector<int>G[maxn*2];
    bool mark[maxn*2];
    int S[maxn*2],c;
    bool dfs(int x)
    {
        if(mark[x^1])return false;
        if(mark[x]) return true;
        mark[x]=true;
        S[c++]=x;
        for(int i=0;i<G[x].size();i++)
            if(!dfs(G[x][i])) return false;
        return true;
    }
    void init(int n)
    {
        this->n=n;
        for(int i=0;i<n*2;i++) G[i].clear();
        memset(mark,0,sizeof(mark));
    }
    void add_clause(int x,int y)
    {
        x=x*2;y=y*2;
        G[x].push_back(y+1);
        G[x+1].push_back(y);
        G[y].push_back(x+1);
        G[y+1].push_back(x);
    }
    bool solve()
    {
        for(int i=0;i<2*n;i+=2)
        {
            if(!mark[i]&&!mark[i+1])
            {
                c=0;
                if(!dfs(i))
                {
                    while(c>0) mark[S[--c]]=false;
                    if(!dfs(i+1)) return false;
                }
            }
        }
        return true;
    }
}solver;
int n,m;
struct Node
{
    int x,y;
}node[600];
bool judge(Node a,Node b)
{
    if(a.x<=b.x&&a.y>=b.y) return false;
    if(a.x>=b.x&&a.y<=b.y) return false;
    if(b.x>=a.y||a.x>=b.y) return false;
    return true;
}
int main()
{
    //freopen("cin.txt","r",stdin);
    while(~scanf("%d%d",&n,&m))
    {
        solver.init(m);
        for(int i=0;i<m;i++)
        {
            scanf("%d%d",&node[i].x,&node[i].y);
            if(node[i].x>node[i].y) swap(node[i].x,node[i].y);
            if(i==0) continue;
            for(int j=0;j<i;j++)
            {
                if(judge(node[i],node[j]))solver.add_clause(i,j);
            }
        }
        if(solver.solve()) puts("panda is telling the truth...");
        else puts("the evil panda is lying again");
    }
    return 0;
}