标签：

Tricks Device

8 9
1 2 2
2 3 2
2 4 1
3 5 3
4 5 4
5 8 1
1 6 2
6 7 5
7 8 1

2 6

最短路，最小割

#include<cstdio>
#include<cstring>
#include<cstdlib>
#include<algorithm>
#include<functional>
#include<iostream>
#include<cmath>
#include<cctype>
#include<ctime>
using namespace std;
#define For(i,n) for(int i=1;i<=n;i++)
#define Fork(i,k,n) for(int i=k;i<=n;i++)
#define Rep(i,n) for(int i=0;i<n;i++)
#define ForD(i,n) for(int i=n;i;i--)
#define RepD(i,n) for(int i=n;i>=0;i--)
#define Forp(x) for(int p=pre[x];p;p=next[p])
#define Forpiter(x) for(int &p=iter[x];p;p=next[p])  
#define Lson (x<<1)
#define Rson ((x<<1)+1)
#define MEM(a) memset(a,0,sizeof(a));
#define MEMI(a) memset(a,127,sizeof(a));
#define MEMi(a) memset(a,128,sizeof(a));
#define INF (2139062143)
#define F (100000007)
#define MAXN (2000+10)
#define MAXM (60000*2+10)
typedef long long ll;
ll mul(ll a,ll b){return (a*b)%F;}
ll add(ll a,ll b){return (a+b)%F;}
ll sub(ll a,ll b){return (a-b+llabs(a-b)/F*F+F)%F;}
void upd(ll &a,ll b){a=(a%F+b%F)%F;}

class Max_flow
{
public:
	int n,s,t;
	int q[MAXN];
	int edge[MAXM],next[MAXM],pre[MAXN],weight[MAXM],size;
	void addedge(int u,int v,int w)
	{
		edge[++size]=v;
		weight[size]=w;
		next[size]=pre[u];	
		pre[u]=size;
	}
	void addedge2(int u,int v,int w){addedge(u,v,w);addedge(v,u,0);}
	bool b[MAXN];
	int d[MAXN];
	bool SPFA(int s,int t)
	{
		For(i,n) d[i]=INF;
		MEM(b)
		d[q[1]=s]=0; b[s]=1;
		int head=1,tail=1;
		while (head<=tail) {
			int now=q[head++];
			Forp(now) {
				int &v=edge[p];
				if (weight[p]&&!b[v])
				{
					d[v]=d[now]+1;
					b[v]=1,q[++tail]=v;
				}
			}
		} 
		return b[t];
	}
	int iter[MAXN];
	int dfs(int x,int f)
	{
		if (x==t) return f;
		Forpiter(x)
		{
			int v=edge[p];
			if (weight[p]&&d[x]<d[v]) 
			{
				int nowflow=dfs(v,min(weight[p],f));
				if (nowflow)
				{
					weight[p]-=nowflow;
					weight[p^1]+=nowflow;
					return nowflow;
				}
			}
		}
		return 0;
	} 
	int max_flow(int s,int t)
	{
		int flow=0;
		while (SPFA(s,t))
		{
			For(i,n) iter[i]=pre[i];
			int f;
			while (f=dfs(s,INF)) flow+=f;
		}
		return flow;
	}
	void mem(int _n,int _s,int _t) { n=_n,s=_s,t=_t; size=1; MEM(pre) }
}S; 
class SPFA
{
public:
	void mem()
	{
		MEM(pre) MEM(edge) MEM(pre) MEM(weight) size=1;
	}
	int q[MAXN*100];
	int edge[MAXM],next[MAXM],pre[MAXN],weight[MAXM],size;
	void addedge(int u,int v,int w)
	{
		edge[++size]=v;
		weight[size]=w;
		next[size]=pre[u];	
		pre[u]=size;
	}
	void addedge2(int u,int v,int w){addedge(u,v,w);addedge(v,u,w);}
	int d[MAXN];
	bool b[MAXN];
	int spfa(int s,int t)
	{
		MEM(b) MEMI(d) 
		b[s]=1; d[s]=0;
		
		int head=1,tail=1;q[1]=1;
		while(head<=tail)
		{
			int now=q[head++];
			b[now]=0;
			Forp(now)
			{
				int v=edge[p];
				if (d[now]+weight[p]<d[v]) {
					d[v]=d[now]+weight[p];
					if (!b[v]) { b[v]=1,q[++tail]=v;
					} 
				}
			}
		}
		return d[t];
	}
}S1,S2;
class link_table
{
public:
	void mem()
	{
		MEM(pre) MEM(edge) MEM(pre) MEM(weight) size=1;
	}
	int q[MAXN*100];
	int edge[MAXM],next[MAXM],pre[MAXN],weight[MAXM],size;
	
	void addedge(int u,int v,int w)
	{
		edge[++size]=v;
		weight[size]=w;
		next[size]=pre[u];	
		pre[u]=size;
	}
	void addedge2(int u,int v,int w){addedge(u,v,w);addedge(v,u,w);}
}St;
int n,m;
int a[MAXM],b[MAXM],l[MAXM];
int main()
{
//	freopen("G.in","r",stdin);
//	freopen(".out","w",stdout);
	while(scanf("%d%d",&n,&m)==2)
	{
		For(i,m) scanf("%d%d%d",&a[i],&b[i],&l[i]);
		S1.mem();
		For(i,m) {
			S1.addedge2(a[i],b[i],l[i]);
		}
		S1.spfa(1,n);
		
		S.mem(n,1,n);
		S2.mem();

		For(i,m) {
			if (S1.d[a[i]]+l[i]==S1.d[b[i]]) S.addedge2(a[i],b[i],1),S2.addedge(a[i],b[i],1);
			else if (S1.d[a[i]]-l[i]==S1.d[b[i]]) S.addedge2(b[i],a[i],1),S2.addedge(b[i],a[i],1);
		}
		
		int t=S.max_flow(1,n);
		cout<<t<<' ';
		cout<<m-S2.spfa(1,n)<<endl;
	}
	return 0;
}

HDU 5294(Tricks Device-最短路最小割)[Template:SPFA]

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原文地址：http://blog.csdn.net/nike0good/article/details/47681791