hdu3572

题解：

网络流

判断是否为漫流

代码:

#include <cstdio>
#include <cstring>
#include <algorithm>
#include <cmath>
#include <cstdlib>
using namespace std;
const int INF=1e9,N=,M=,FIN=;
typedef long long ll;
int n,m,s,t,sum,ec,head[N],first[N],que[N],lev[N],Next[M],to[M],v[M];
void init()
{
    sum=ec=;
    memset(first,-,sizeof(first));
    s=,t=FIN;
}
void addEdge(int a,int b,int c)
{
    to[ec]=b;
    v[ec]=c;
    Next[ec]=first[a];
    first[a]=ec++;
    to[ec]=a;
    v[ec]=;
    Next[ec]=first[b];
    first[b]=ec++;
}
int BFS()
{
    int kid,now,f=,r=;
    memset(lev,,sizeof(lev));
    que[]=s,lev[s]=;
    while (f<r)
     {
        now=que[f++];
        for (int i=first[now];i!=-;i=Next[i])
         {
            kid=to[i];
            if (!lev[kid]&&v[i])
             {
                lev[kid]=lev[now]+;
                if (kid==t)return ;
                que[r++]=kid;
             }
         }
     }
    return ;
}
int DFS(int now, int sum)
{
    int kid,flow,rt=;
    if (now==t) return sum;
    for (int i=head[now];i!=-&&rt<sum;i=Next[i])
     {
        head[now]=i;
        kid=to[i];
        if (lev[kid]==lev[now]+&&v[i])
         {
            flow=DFS(kid,min(sum-rt,v[i]));
            if (flow)
             {
                v[i]-=flow;
                v[i^]+=flow;
                rt+=flow;
             }
            else lev[kid]=-;
         }
     }
    return rt;
}
int dinic()
{
    int ans=;
    while (BFS())
     {
        for (int i=;i<=t;i++)head[i]=first[i];
        ans+=DFS(s,INF);
     }
    return ans;
}
void input()
{
    int Min=INF,Max=;
    scanf("%d%d",&n,&m);
    int a,b,c;
    for (int i=;i<=n;i++)
     {
        scanf("%d%d%d",&a,&b,&c);
        sum+=a;
        addEdge(s,i,a);
        for (int j=b;j<=c;j++)addEdge(i,j+n,);
        if (c<b)swap(c,b);
        if (Min>b)Min=b;
        if (Max<c)Max=c;
     }
    for (int i=Min;i<=Max;i++)addEdge(i+n,t,m);
}
int main()
{
    int T,Case=;
    scanf("%d",&T);
    while (T--)
     {
        printf("Case %d: ",Case++);
        init();
        input();
        if (dinic()==sum) puts("Yes");
        else puts("No");
        puts("");
     }
    return ;
}