网络最大流 复习

哎

打板子 调了\(2\)h 无语了

\(EdmondKarp+Dinic(Dinitz)\)

#include <set>
#include <stack>
#include <queue>
#include <cstdio>
#include <cstring>
#include <iostream>
#include <algorithm>
using namespace std;
#define reg register int
#define isdigit(x) ('0' <= x&&x <= '9')
template<typename T>
inline T Read(T Type)
{
	T x = 0,f = 1;
	char a = getchar();
	while(!isdigit(a)) {if(a == '-') f = -1;a = getchar();}
	while(isdigit(a)) {x = (x << 1) + (x << 3) + (a ^ '0');a = getchar();}
	return x * f;
}
const int MAXN = 10010,MAXM = 100010;
int cnt,n,m,s,t,_ori[MAXN];
struct EDGE
{
	int v,w,_nxt;
	EDGE() {v = w = _nxt = 0;}
}edge[MAXM << 1];
inline void addedge(int u,int v,int w)
{
	edge[++cnt]._nxt = _ori[u];
	edge[cnt].v = v;
	edge[cnt].w = w;	
	_ori[u] = cnt;
}
inline void add(int u,int v,int w) {addedge(u,v,w),addedge(v,u,0);}
namespace EdmondKarp
{
	const int inf = 0x7f7f7f7f;
	struct Path {int v,e;}pre[MAXN];
	bool vis[MAXN];
	inline bool Bfs(int s,int t)
	{
		memset(vis,0,sizeof(vis));
		memset(pre,0,sizeof(pre));
		queue<int> q;
		q.push(s),vis[s] = 1;
		while(!q.empty())
		{
			int v,tp = q.front();q.pop();
			if(tp == t) return true;
			for(reg e = _ori[tp];e;e = edge[e]._nxt)
				if(!vis[v = edge[e].v]&&edge[e].w)
				{
					pre[v].v = tp,pre[v].e = e;
					if(v == t) return true;
					vis[v] = 1,q.push(v);
				}
		}
		return false;
	}
	inline int EK(int s,int t)
	{
		int ans = 0;
		while(Bfs(s,t))
		{
			int flow_ = inf;
			for(reg i = t;i != s;flow_ = min(flow_,edge[pre[i].e].w),i = pre[i].v);
			for(reg i = t;i != s;edge[pre[i].e].w -= flow_,edge[pre[i].e ^ 1].w += flow_,i = pre[i].v);
			ans += flow_;
		}
		return ans;
	}
}
namespace Dinitz
{
	const int inf = 0x7f7f7f7f;
	int depth[MAXN],fire[MAXN];
	inline bool Bfs(int s,int t)
	{
		memset(depth,-1,sizeof(depth));
		queue<int> q;
		q.push(s),depth[s] = 0;
		while(!q.empty())
		{
			int v,tp = q.front();q.pop();
			for(reg e = _ori[tp];e;e = edge[e]._nxt)
				if(depth[v = edge[e].v] == -1&&edge[e].w)
					depth[v] = depth[tp] + 1,q.push(v);
		}
		return (depth[t] != -1);
	}
	inline int dfs(int x,int t,int _flow)
	{
		if(x == t) return _flow; int v,flow_ = 0;
		for(reg e = fire[x];e;e = edge[e]._nxt)
		{
			fire[x] = e;
			if(depth[v = edge[e].v] == depth[x] + 1&&edge[e].w)
			{
				int flow = dfs(v,t,min(_flow,edge[e].w));
				_flow -= flow,flow_ += flow;
				edge[e].w -= flow,edge[e ^ 1].w += flow;
				if(!_flow) break;
			}
		}
		if(!flow_) depth[x] = -1;
		return flow_;
	}
	inline int Dinic(int s,int t)
	{
		int ans = 0;
		while(Bfs(s,t))
		{
			for(reg i = 1;i <= n;i++) fire[i] = _ori[i];
			ans += dfs(s,t,inf);
		}
		return ans;
	}
}
int main()
{
	cnt = 1;
	n = Read(1),m = Read(1),s = Read(1),t = Read(1);
	for(reg i = 1;i <= m;i++)
	{
		int u = Read(1),v = Read(1),w = Read(1);
		add(u,v,w);
	}
	int ans = Dinitz::Dinic(s,t);
	printf("%d",ans);
	return 0;
}

例题P1343 地震逃生

#include <set>
#include <stack>
#include <queue>
#include <cstdio>
#include <cstring>
#include <iostream>
#include <algorithm>
using namespace std;
#define reg register int
#define isdigit(x) ('0' <= x&&x <= '9')
template<typename T>
inline T Read(T Type)
{
	T x = 0,f = 1;
	char a = getchar();
	while(!isdigit(a)) {if(a == '-') f = -1;a = getchar();}
	while(isdigit(a)) {x = (x << 1) + (x << 3) + (a ^ '0');a = getchar();}
	return x * f;
}
const int MAXN = 220,MAXM = 2010;
int cnt,n,m,s,t,_ori[MAXN];
typedef long long ll;
struct EDGE
{
	int v,_nxt;ll w;
	EDGE() {v = w = _nxt = 0;}
}edge[MAXM << 2];
inline void addedge(int u,int v,ll w)
{
	edge[++cnt]._nxt = _ori[u];
	edge[cnt].v = v;
	edge[cnt].w = w;	
	_ori[u] = cnt;
}
inline void add(int u,int v,ll w) {addedge(u,v,w),addedge(v,u,0ll);}
namespace EdmondKarp
{
	const int inf = 0x7f7f7f7f;
	struct Path {int v,e;}pre[MAXN];
	bool vis[MAXN];
	inline bool Bfs(int s,int t)
	{
		memset(vis,0,sizeof(vis));
		memset(pre,0,sizeof(pre));
		queue<int> q;
		q.push(s),vis[s] = 1;
		while(!q.empty())
		{
			int v,tp = q.front();q.pop();
			if(tp == t) return true;
			for(reg e = _ori[tp];e;e = edge[e]._nxt)
				if(!vis[v = edge[e].v]&&edge[e].w)
				{
					pre[v].v = tp,pre[v].e = e;
					if(v == t) return true;
					vis[v] = 1,q.push(v);
				}
		}
		return false;
	}
	inline ll EK(int s,int t)
	{
		ll ans = 0;
		while(Bfs(s,t))
		{
			ll flow_ = inf;
			for(reg i = t;i != s;flow_ = min(flow_,edge[pre[i].e].w),i = pre[i].v);
			for(reg i = t;i != s;edge[pre[i].e].w -= flow_,edge[pre[i].e ^ 1].w += flow_,i = pre[i].v);
			ans += flow_;
		}
		return ans;
	}
}
int main()
{
	cnt = 1;
	ll stu;
	n = Read(1),m = Read(1),stu = Read(1ll);
	for(reg i = 1;i <= m;i++)
	{
		int u = Read(1),v = Read(1),w = Read(1);
		add(u,v,w);
	}
	ll ans = EdmondKarp::EK(1,n);
	if(ans == 0) printf("Orz Ni Jinan Saint Cow!");
	else printf("%lld %lld",ans,(stu / ans + (stu % ans?1:0)));
	return 0;
}

P1345 [USACO5.4]奶牛的电信Telecowmunication

#include <set>
#include <stack>
#include <queue>
#include <cstdio>
#include <cstring>
#include <iostream>
#include <algorithm>
using namespace std;
#define reg register int
#define isdigit(x) ('0' <= x&&x <= '9')
template<typename T>
inline T Read(T Type)
{
	T x = 0,f = 1;
	char a = getchar();
	while(!isdigit(a)) {if(a == '-') f = -1;a = getchar();}
	while(isdigit(a)) {x = (x << 1) + (x << 3) + (a ^ '0');a = getchar();}
	return x * f;
}
const int MAXN = 220,MAXM = 2010;
int cnt,n,m,s,t,_ori[MAXN];
typedef long long ll;
struct EDGE
{
	int v,_nxt;ll w;
	EDGE() {v = w = _nxt = 0;}
}edge[MAXM << 2];
inline void addedge(int u,int v,ll w)
{
	edge[++cnt]._nxt = _ori[u];
	edge[cnt].v = v;
	edge[cnt].w = w;	
	_ori[u] = cnt;
}
inline void add(int u,int v,ll w) {addedge(u,v,w),addedge(v,u,0ll);}
const int inf = 0x7f7f7f7f;
namespace EdmondKarp
{
	struct Path {int v,e;}pre[MAXN];
	bool vis[MAXN];
	inline bool Bfs(int s,int t)
	{
		memset(vis,0,sizeof(vis));
		memset(pre,0,sizeof(pre));
		queue<int> q;
		q.push(s),vis[s] = 1;
		while(!q.empty())
		{
			int v,tp = q.front();q.pop();
			if(tp == t) return true;
			for(reg e = _ori[tp];e;e = edge[e]._nxt)
				if(!vis[v = edge[e].v]&&edge[e].w)
				{
					pre[v].v = tp,pre[v].e = e;
					if(v == t) return true;
					vis[v] = 1,q.push(v);
				}
		}
		return false;
	}
	inline ll EK(int s,int t)
	{
		ll ans = 0;
		while(Bfs(s,t))
		{
			ll flow_ = inf;
			for(reg i = t;i != s;flow_ = min(flow_,edge[pre[i].e].w),i = pre[i].v);
			for(reg i = t;i != s;edge[pre[i].e].w -= flow_,edge[pre[i].e ^ 1].w += flow_,i = pre[i].v);
			ans += flow_;
		}
		return ans;
	}
}
int main()
{
	cnt = 1;
	n = Read(1),m = Read(1),s = Read(1),t = Read(1);
	for(reg i = 1;i <= n;i++)
		if(i == s||i == t) add(i,n + i,inf);
		else add(i,n + i,1);
	for(reg i = 1;i <= m;i++)
	{
		int u = Read(1),v = Read(1);
		add(u + n,v,inf),add(v + n,u,inf);
	}
	ll ans = EdmondKarp::EK(s,t);
	printf("%d",ans);
	return 0;
}