poj 3683 Priest John's Busiest Day

题目链接:http://poj.org/problem?id=3683

题目大意:给定每场婚礼的起始时间(s~T),而且每次婚礼必须在开头或结尾(二选一)花D时间用来主持( [S,S+D) 或[T-D,T) ),而且主持不能同时进行,问是否存在一种方案使得所有婚礼均能被主持,能的话把方案输出.

题目思路:2-SAT问题,完整的2-SAT算法(详见http://wenku.baidu.com/view/6a6d38000740be1e650e9a6b.html).

代码:

#include <stdlib.h>#include <string.h>#include <stdio.h>#include <ctype.h>#include <math.h>#include <time.h>#include <stack>#include <queue>#include <map>#include <set>#include <vector>#include <string>#include <iostream>#include <algorithm>using namespace std;#define ull unsigned __int64//#define ll __int64//#define ull unsigned long long#define ll long long#define son1 New(p.xl,xm,p.yl,ym),(rt<<2)-2#define son2 New(p.xl,xm,min(ym+1,p.yr),p.yr),(rt<<2)-1#define son3 New(min(xm+1,p.xr),p.xr,p.yl,ym),rt<<2#define son4 New(min(xm+1,p.xr),p.xr,min(ym+1,p.yr),p.yr),rt<<2|1#define lson l,mid,rt<<1#define rson mid+1,r,rt<<1|1#define middle (l+r)>>1#define MOD 1000000007#define esp (1e-8)const int INF=0x3F3F3F3F;const double DINF=10000.00;//const double pi=acos(-1.0);const int M=2010;int min(int x,int y){return x<y? x:y;}int max(int x,int y){return x>y? x:y;}void swap(int& x,int& y){int t=x;x=y;y=t;}int T,cas;vector<int>init[M],now[M];int low[M],pre[M],idx[M],ss[M],Hash[M],sym[M];int n,nn,Index,top,m,N,deg[M];struct node{int s,t;}pot[M];void dfs(int u){low[u]=pre[u]=++Index;ss[++top]=u;for(int i=0;i<init[u].size();i++){int v=init[u][i];if(pre[v]==-1) dfs(v),low[u]=min(low[u],low[v]);else if(idx[v]==-1) low[u]=min(low[u],pre[v]);}if(low[u]==pre[u]){int v=-1;now[++nn].clear();while(u!=v) idx[v=ss[top--]]=nn;}}void Tarjan(){memset(idx,-1,sizeof(int)*(n+1));memset(pre,-1,sizeof(int)*(n+1));Index=top=nn=0,ss[0]=-1;for(int u=1;u<=n;u++) if(pre[u]==-1) dfs(u);}void shrink(){memset(deg,0,sizeof(int)*(nn+1));memset(Hash,-1,sizeof(int)*(nn+1));for(int u=1;u<=nn;u++){for(int i=0;i<init[u].size();i++){int v=init[u][i];if(idx[u]!=idx[v] /*&& Hash[idx[u]]!=idx[v]*/){//Hash[idx[u]]=idx[v];now[idx[v]].push_back(idx[u]);deg[idx[u]]++;}}}}bool isCross(int i,int j){if(pot[i].s<pot[j].t && pot[j].s<pot[i].t) return true;return false;}struct cmp{bool operator () (int a,int b){return a > b;}};void _sof(){Tarjan();for(int i=1;i<=n;i+=2){if(idx[i]==idx[i+1]){puts("NO");return;}sym[idx[i]]=idx[i+1],sym[idx[i+1]]=idx[i];}puts("YES");shrink();for(int i=1;i<=nn;i++) if(!deg[i]) ss[++top]=i,deg[i]=-1,deg[sym[i]]=-2;while(top){int u=ss[top--];for(int i=0;i<now[u].size();i++){int v=now[u][i];if(--deg[v]==0) ss[++top]=v,deg[v]=-1,deg[sym[v]]=-2;}}for(int i=1;i<=n;i++) if(deg[idx[i]]==-1){int sh,sm,th,tm;sh=pot[i].s/60,sm=pot[i].s%60;th=pot[i].t/60,tm=pot[i].t%60;printf("%02d:%02d %02d:%02d\n",sh,sm,th,tm);}}void _init(){int i,j,sh,sm,th,tm,d,u,uu,v,vv;for(i=0;i<N;i++){scanf("%d:%d %d:%d %d",&sh,&sm,&th,&tm,&d);u=i<<1|1,uu=u+1;pot[u].s=sh*60+sm,pot[uu].t=th*60+tm;pot[u].t=pot[u].s+d,pot[uu].s=pot[uu].t-d;}for(u=1,n=N<<1;u<=n;u++) init[u].clear();for(u=1;u<=n;u++){uu= u&1? u+1:u-1;for(v=1;v<=n;v++) if(v!=u && v!=uu){vv= v&1? v+1:v-1;if(isCross(u,v)) init[u].push_back(vv);}}_sof();}int main(){//freopen("1.in","r",stdin);//freopen("1.out","w",stdout);//_init()//scanf("%d",&T);for(cas=1;cas<=T;cas++) _init();while(~scanf("%d",&N))  _init();return 0;}