poj 3683(2-sat+拓扑排序）

Priest John's Busiest Day

Time Limit: 2000MS		Memory Limit: 65536K
Total Submissions: 11127		Accepted: 3785		Special Judge

Description

John is the only priest in his town. September 1st is the John's busiest day in a year because there is an old legend in the town that the couple who get married on that day will be forever blessed by the God of Love. This year N couples plan to get married on the blessed day. The i-th couple plan to hold their wedding from time S_i to time T_i. According to the traditions in the town, there must be a special ceremony on which the couple stand before the priest and accept blessings. The i-th couple need D_i minutes to finish this ceremony. Moreover, this ceremony must be either at the beginning or the ending of the wedding (i.e. it must be either from S_i to S_i + D_i, or from T_i - D_i to T_i). Could you tell John how to arrange his schedule so that he can present at every special ceremonies of the weddings.

Note that John can not be present at two weddings simultaneously.

Input

The first line contains a integer N ( 1 ≤ N ≤ 1000).
The next N lines contain the S_i, T_i and D_i. S_i and T_i are in the format of hh:mm.

Output

The first line of output contains "YES" or "NO" indicating whether John can be present at every special ceremony. If it is "YES", output another N lines describing the staring time and finishing time of all the ceremonies.

Sample Input

2
08:00 09:00 30
08:15 09:00 20

Sample Output

YES
08:00 08:30
08:40 09:00

Source

POJ Founder Monthly Contest – 2008.08.31, Dagger and Facer

将每个时间段拆分成两个 就变成的2-sat模型

利用拓扑排序+染色输出任意方案就可以了

注意数组大小

#include<iostream>
#include<cstdio>
#include<cstdlib>
#include<cctype>
#include<cmath>
#include<cstring>
#include<map>
#include<queue>
#include<stack>
#include<set>
#include<vector>
#include<algorithm>
#include<string.h>
typedef long long ll;
typedef unsigned long long LL;
using namespace std;
const int INF=0x3f3f3f3f;
const double eps=0.0000000001;
const int N=2000+10;
const ll mod=1e9+7;
struct Node{
    int x,y;
}a[N];
struct node{
    int to,next;
}edge[N*N];
struct NODE{
    int to,next;
}Edge[N*N];
int Head[N];
int head[N],low[N],dfn[N];
int vis[N*10],belong[N*10];
int opp[N*10];
int cnt,t,tot;
stack<int>st;
void init(){
    tot=0;
    t=0;
    cnt=0;
    memset(belong,-1,sizeof(belong));
    memset(low,0,sizeof(low));
    memset(dfn,0,sizeof(dfn));
    memset(vis,0,sizeof(vis));
    memset(head,-1,sizeof(head));
}
void add(int u,int v){
    edge[tot].to=v;
    edge[tot].next=head[u];
    head[u]=tot++;
}
void ADD(int u,int v){
    Edge[tot].to=v;
    Edge[tot].next=Head[u];
    Head[u]=tot++;
}
void tarjan(int u){
    vis[u]=1;
    st.push(u);
    dfn[u]=low[u]=++t;
    for(int i=head[u];i!=-1;i=edge[i].next){
        int v=edge[i].to;
        if(dfn[v]==0){
            tarjan(v);
            low[u]=min(low[u],low[v]);
        }
        else if(vis[v]){
            low[u]=min(low[u],dfn[v]);
        }
    }
    if(low[u]==dfn[u]){
        cnt++;
        int vv;
        do{
            vv=st.top();
            st.pop();
            belong[vv]=cnt;
            vis[vv]=0;
        }while(vv!=u);
    }
}
int n;
int in[N];
void topsort(){
    queue<int>q;
    memset(vis,0,sizeof(vis));
    for(int i=1;i<=cnt;i++)if(in[i]==0)q.push(i);
    while(q.empty()==0){
        int u=q.front();
        q.pop();
        if(vis[u]==0){
            vis[u]=1;
            vis[opp[u]]=-1;
        }
        for(int i=Head[u];i!=-1;i=Edge[i].next){
            int v=Edge[i].to;
            in[v]--;
            if(in[v]==0){
                q.push(v);
            }
        }
    }
}
int check(int i,int j){
    if(a[i].y<=a[j].x){
       return 1;
    }

    if(a[i].x>=a[j].y){
        return 1;
    }
    return 0;
}
char str1[100];
char str2[100];
int main(){
    while(scanf("%d",&n)!=EOF){
        int val;
        init();
        memset(in,0,sizeof(in));
        for(int i=0;i<(n<<1);i=i+2){
           scanf("%s%s%d",str1,str2,&val);
           int x=(str1[0]-'0')*60*10+(str1[1]-'0')*60+(str1[3]-'0')*10+str1[4]-'0';
           int y=(str2[0]-'0')*60*10+(str2[1]-'0')*60+(str2[3]-'0')*10+str2[4]-'0';;
           a[i].x=x;
           a[i].y=x+val;
           a[i+1].x=y-val;
           a[i+1].y=y;
        }
        for(int i=0;i<(n<<1);i=i+2){
            for(int j=0;j<(n<<1);j=j+2){
                if(i==j)continue;
                if(check(i,j)==0)add(i,j^1);
                if(check(i,j^1)==0)add(i,j);
                if(check(i^1,j)==0)add(i^1,j^1);
                if(check(i^1,j^1)==0)add(i^1,j);
            }
        }
        for(int i=0;i<(n<<1);i++){
            if(dfn[i]==0)tarjan(i);
        }
        int flag=0;
        for(int i=0;i<(n<<1);i=i+2){
            opp[belong[i]]=belong[i^1];
            opp[belong[i^1]]=belong[i];
            if(belong[i]==belong[i^1])flag=1;
        }
        if(flag){
            cout<<"NO"<<endl;
            continue;
        }
        cout<<"YES"<<endl;
        memset(Head,-1,sizeof(Head));
        tot=0;
        for(int u=0;u<(n<<1);u++){
            for(int i=head[u];i!=-1;i=edge[i].next){
                int v=edge[i].to;
                if(belong[u]!=belong[v]){
                    ADD(belong[v],belong[u]);
                    in[belong[u]]++;
                }
            }
        }

        topsort();
        int aa,b,c,d;
        for(int i=0;i<n;i++){
            if(vis[belong[i<<1]]==1){
                aa=a[i*2].x/60;
                b=a[i*2].x%60;
                c=a[i*2].y/60;
                d=a[i*2].y%60;
                //cout<<a[i*2].x<<" "<<a[i*2].y<<endl;
                printf("%02d:%02d %02d:%02d\n",aa,b,c,d);
            }
            else{
                aa=a[i*2+1].x/60;
                b=a[i*2+1].x%60;
                c=a[i*2+1].y/60;
                d=a[i*2+1].y%60;
                //cout<<a[i*2+1].x<<" "<<a[i*2+1].y<<endl;
                printf("%02d:%02d %02d:%02d\n",aa,b,c,d);
            }
        }
    }
}