poj 3683 Priest John's Busiest Day 2-sat

 

#include<cstdio>
#include<algorithm>
#include<vector>
#include<cstring>
#include<stack>
using namespace std;

const int maxn = 2000 + 30;

vector<int> G[maxn], G2[maxn];
vector<int> S;
int vis[maxn], sccno[maxn], scc_cnt;
int n,m;
int s[maxn],t[maxn],d[maxn];

void dfs1(int u)
{
    if(vis[u]) return;
    vis[u] = 1;
    for(int i = 0; i < G[u].size(); i++) dfs1(G[u][i]);
    S.push_back(u);
}

void dfs2(int u)
{
    if(sccno[u]) return;
    sccno[u] = scc_cnt;
    for(int i = 0; i < G2[u].size(); i++) dfs2(G2[u][i]);
}

void find_scc(int n)
{
    int i;
    scc_cnt = 0;
    S.clear();
    memset(sccno, 0, sizeof(sccno));
    memset(vis, 0, sizeof(vis));
    for(i = 0; i < n; i++) dfs1(i);
    for(i = n-1; i >= 0; i--)
    if(!sccno[S[i]]) { scc_cnt++; dfs2(S[i]); }
}

int main()
{
    while(scanf("%d",&n)!=EOF)
    {
        int i,j;
        int x,y;
        for(i=0;i<2*n;i++)
        {
            G[i].clear();
            G2[i].clear();
        }
        for(i=0;i<n;i++)
        {
            scanf("%d:%d",&x,&y);
            s[i]=x*60+y;
            scanf("%d:%d",&x,&y);
            t[i]=x*60+y;
            scanf("%d",&d[i]);
        }
        for(i=0;i<n;i++)
            for(j=i+1;j<n;j++)
            {
                if( !( s[j]>=s[i]+d[i] || s[j]+d[j]<=s[i] ) )
                {
                    G[i].push_back(j+n); G2[j+n].push_back(i);
                    G[j].push_back(i+n); G2[i+n].push_back(j);
                }
                if( !( t[j]-d[j]>=s[i]+d[i] || t[j]<=s[i] ) )
                {
                    G[i].push_back(j); G2[j].push_back(i);
                    G[j+n].push_back(i+n); G2[i+n].push_back(j+n);
                }
                if( !( t[j]-d[j]>=t[i] || t[j]<=t[i]-d[i] ) )
                {
                    G[i+n].push_back(j); G2[j].push_back(i+n);
                    G[j+n].push_back(i); G2[i].push_back(j+n);
                }
                if( !( t[i]-d[i]>=s[j]+d[j] || t[i]<=s[j] ) )
                {
                    G[i+n].push_back(j+n); G2[j+n].push_back(i+n);
                    G[j].push_back(i); G2[i].push_back(j);
                }
            }
        find_scc(2*n);
        int flag=1;
        for(i=0;i<n;i++)
        {
            if(sccno[i]==sccno[i+n])
            {
                printf("NO\n");
                flag=0;
                break;
            }
        }
        if(flag)
        {
            printf("YES\n");
            for(i=0;i<n;i++)
            {
                if(sccno[i]>sccno[i+n])
                    printf("%02d:%02d %02d:%02d\n",s[i]/60,s[i]%60,(s[i]+d[i])/60,(s[i]+d[i])%60);
                else printf("%02d:%02d %02d:%02d\n",(t[i]-d[i])/60,(t[i]-d[i])%60,t[i]/60,t[i]%60);
            }
        }
    }
    return 0;
}