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=2500,M=400005,FIN=2015;
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=0;
    memset(first,-1,sizeof(first));
    s=0,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]=0;
    Next[ec]=first[b];
    first[b]=ec++;
}
int BFS() 
{
    int kid,now,f=0,r=1;
    memset(lev,0,sizeof(lev));
    que[0]=s,lev[s]=1;
    while (f<r)
     {
        now=que[f++];
        for (int i=first[now];i!=-1;i=Next[i])
         {
            kid=to[i];    
            if (!lev[kid]&&v[i])
             {
                lev[kid]=lev[now]+1;    
                if (kid==t)return 1;
                que[r++]=kid;
             }
         }
     }
    return 0;
}
int DFS(int now, int sum) 
{
    int kid,flow,rt=0;
    if (now==t) return sum;
    for (int i=head[now];i!=-1&&rt<sum;i=Next[i])
     {
        head[now]=i;  
        kid=to[i];
        if (lev[kid]==lev[now]+1&&v[i])
         {
            flow=DFS(kid,min(sum-rt,v[i]));
            if (flow)
             {
                v[i]-=flow;
                v[i^1]+=flow;
                rt+=flow;
             }
            else lev[kid]=-1;   
         }           
     }
    return rt;
}
int dinic() 
{
    int ans=0;
    while (BFS())
     {
        for (int i=0;i<=t;i++)head[i]=first[i]; 
        ans+=DFS(s,INF);
     }
    return ans;
}   
void input() 
{
    int Min=INF,Max=0;
    scanf("%d%d",&n,&m);
    int a,b,c;
    for (int i=1;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,1);   
        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=1;
    scanf("%d",&T);
    while (T--)
     {
        printf("Case %d: ",Case++);
        init();
        input();
        if (dinic()==sum) puts("Yes");
        else puts("No");
        puts("");
     }
    return 0;
}