Artifact b357fd2040b9449a5148cbba3e66c95a567f84ea

• File SRM/399/1C.cpp
  • 2011-02-23 09:21:16 - part of checkin [4fd800b3a8] on branch trunk - Copied from private svn repository. (user: kinaba) [annotate]

#include <vector>
#include <string>
#include <iostream>
#include <cstring>
using namespace std;




static const int NV = 512;
typedef int           flow;
typedef int           vert;
typedef vert          edge;
typedef vector<edge>  edges;
typedef vector<edges> graph;
typedef flow          flow_graph[NV][NV];

flow dinic_dfs( graph& G, flow_graph F, vert v, vert D,
                int LV[], flow flow_in, int blocked[] )
{
	flow flow_out = 0;
	for(int i=0; i!=G[v].size(); ++i)
	{
		int u = G[v][i];
		if( LV[v]+1==LV[u] && F[v][u] )
		{
			flow f = min(flow_in-flow_out, F[v][u]);
			if( u==D || !blocked[u] && (f=dinic_dfs(G,F,u,D,LV,f,blocked)) )
			{
				F[v][u]  -= f;
				F[u][v]  += f;
				flow_out += f;
				if( flow_in == flow_out ) return flow_out;
			}
		}
	}
	blocked[v] = (flow_out==0);
	return flow_out;
}

flow dinic( graph& G, flow_graph F, vert S, vert D )
{
	for( flow total=0 ;; ) {
		int LV[NV] = {0};
		vector<int> Q(1, S);
		for(int lv=1; !Q.empty(); ++lv)
		{
			vector<int> Q2;
			for(int i=0; i!=Q.size(); ++i)
			{
				edges& ne = G[Q[i]];
				for(int j=0; j!=ne.size(); ++j)
					if( F[Q[i]][ne[j]] && !LV[ne[j]] && ne[j]!=S )
						LV[ne[j]]=lv, Q2.push_back(ne[j]);
			}
			Q.swap(Q2);
		}

		if( !LV[D] )
			return total;

		int blocked[NV] = {};
		total += dinic_dfs( G, F, S, D, LV, 0x7fffffff, blocked );
	}
}



struct DancingParty
{
	int maxDances(vector<string> likes, int k)
	{
		int n = likes.size();
		#define SRC 0
		#define DST 1
		#define L(i)  2+n*0+i
		#define R(i)  2+n*1+i
		#define YL(i) 2+n*2+i
		#define NL(i) 2+n*3+i
		#define YR(i) 2+n*4+i
		#define NR(i) 2+n*5+i

		graph G(2+n*6);

		// Graph
		for(int i=0; i<n; ++i) {
			G[SRC ].push_back(L(i));  G[L(i) ].push_back(SRC);
			G[L(i)].push_back(YL(i)); G[YL(i)].push_back(L(i));
			G[L(i)].push_back(NL(i)); G[NL(i)].push_back(L(i));

			G[DST ].push_back(R(i));  G[R(i) ].push_back(DST);
			G[R(i)].push_back(YR(i)); G[YR(i)].push_back(R(i));
			G[R(i)].push_back(NR(i)); G[NR(i)].push_back(R(i));

			for(int j=0; j<n; ++j)
				if( likes[i][j] == 'Y' )
					G[YL(i)].push_back(YR(j)), G[YR(j)].push_back(YL(i));
				else
					G[NL(i)].push_back(NR(j)), G[NR(j)].push_back(NL(i));
		}

		for(int M=1; M<=n; ++M) {
			// Flow
			flow_graph F = {};
			for(int i=0; i<n; ++i) {
				F[SRC][L(i)] = M;
				F[L(i)][YL(i)] = M;
				F[L(i)][NL(i)] = k;

				F[R(i)][DST] = M;
				F[YR(i)][R(i)] = M;
				F[NR(i)][R(i)] = k;

				for(int j=0; j<n; ++j)
					if( likes[i][j] == 'Y' )
						F[YL(i)][YR(j)] = 1;
					else
						F[NL(i)][NR(j)] = 1;
			}

			// Maxflow
			if( dinic(G, F, SRC, DST) < M*n )
				return M-1;
		}
		return n;
	}
};