// -*- C++ -*-

/*

preflow_push_hl.hh

by jacint. 

Runs the highest label variant of the preflow push algorithm with 

running time O(n^2\sqrt(m)). 

Member functions:

void run() : runs the algorithm

 The following functions should be used after run() was already run.

T maxflow() : returns the value of a maximum flow

T flowonEdge(Edge_iterator e) : for a fixed maximum flow x it returns x(e) 

EdgeMap<graph_type, T> allflow() : returns the fixed maximum flow x

NodeMap<graph_type, bool> mincut() : returns a 

     characteristic vector of a minimum cut. (An empty level 

     in the algorithm gives a minimum cut.)

*/

#ifndef PREFLOW_PUSH_HL_H

#define PREFLOW_PUSH_HL_H

#include <algorithm>

#include <vector>

#include <stack>

#include <reverse_bfs.h>

namespace marci {

  template <typename Graph, typename T>

  class preflow_push_hl {

    typedef typename Graph::NodeIt NodeIt;

    typedef typename Graph::EdgeIt EdgeIt;

    typedef typename Graph::EachNodeIt EachNodeIt;

    typedef typename Graph::OutEdgeIt OutEdgeIt;

    typedef typename Graph::InEdgeIt InEdgeIt;

    typedef typename Graph::EachEdgeIt EachEdgeIt;

    Graph& G;

    NodeIt s;

    NodeIt t;

    typename Graph::EdgeMap<T> flow;

    typename Graph::EdgeMap<T> capacity; 

    T value;

    typename Graph::NodeMap<bool> mincutvector;

  public:

    preflow_push_hl(Graph& _G, NodeIt _s, NodeIt _t, 

		    typename Graph::EdgeMap<T>& _capacity) :

      G(_G), s(_s), t(_t), flow(_G, 0), capacity(_capacity), mincutvector(_G, true) { }

    /*

      The run() function runs the highest label preflow-push, 

      running time: O(n^2\sqrt(m))

    */

    void run() {

      typename Graph::NodeMap<int> level(G);         //level of Node

      typename Graph::NodeMap<T> excess(G);          //excess of Node

      int n=G.nodeNum();                        //number of Nodes 

      int b=n; 

      /*b is a bound on the highest level of an active Node. In the beginning it is at most n-2.*/

      std::vector<std::stack<NodeIt> > stack(2*n-1);    //Stack of the active Nodes in level i.

      /*Reverse_bfs from t, to find the starting level.*/

      reverse_bfs<Graph> bfs(G, t);

      bfs.run();

      for(EachNodeIt v=G.template first<EachNodeIt>(); v.valid(); ++v) {

	level.set(v, bfs.dist(v)); 

	//std::cout << "the level of " << v << " is " << bfs.dist(v);

      }

      /*The level of s is fixed to n*/ 

      level.set(s,n);

      /* Starting flow. It is everywhere 0 at the moment. */

      for(OutEdgeIt i=G.template first<OutEdgeIt>(s); i.valid(); ++i) 

	{

	  NodeIt w=G.head(i);

	  flow.set(i, capacity.get(i)); 

	  stack[bfs.dist(w)].push(w); 

	  excess.set(w, capacity.get(i));

	}

      /* 

	 End of preprocessing 

      */

      /*

	Push/relabel on the highest level active Nodes.

      */

      /*While there exists active Node.*/

      while (b) { 

	/*We decrease the bound if there is no active Node of level b.*/

	if (stack[b].empty()) {

	  --b;

	} else {

	  NodeIt w=stack[b].top();    //w is the highest label active Node.

	  stack[b].pop();                    //We delete w from the stack.

	  int newlevel=2*n-2;                   //In newlevel we maintain the next level of w.

	  for(OutEdgeIt e=G.template first<OutEdgeIt>(w); e.valid(); ++e) {

	    NodeIt v=G.head(e);

	    /*e is the Edge wv.*/

	    if (flow.get(e)<capacity.get(e)) {              

	      /*e is an Edge of the residual graph */

	      if(level.get(w)==level.get(v)+1) {      

		/*Push is allowed now*/

		if (capacity.get(e)-flow.get(e) > excess.get(w)) {       

		  /*A nonsaturating push.*/

		  if (excess.get(v)==0 && v != s) stack[level.get(v)].push(v); 

		  /*v becomes active.*/

		  flow.set(e, flow.get(e)+excess.get(w));

		  excess.set(v, excess.get(v)+excess.get(w));

		  excess.set(w,0);

		  //std::cout << w << " " << v <<" elore elen nonsat pump "  << std::endl;

		  break; 

		} else { 

		  /*A saturating push.*/

		  if (excess.get(v)==0 && v != s) stack[level.get(v)].push(v); 

		  /*v becomes active.*/

		  excess.set(v, excess.get(v)+capacity.get(e)-flow.get(e));

		  excess.set(w, excess.get(w)-capacity.get(e)+flow.get(e));

		  flow.set(e, capacity.get(e));

		  //std::cout << w<<" " <<v<<" elore elen sat pump "   << std::endl;

		  if (excess.get(w)==0) break;

		  /*If w is not active any more, then we go on to the next Node.*/

		} // if (capacity.get(e)-flow.get(e) > excess.get(w))

	      } // if(level.get(w)==level.get(v)+1)

	      else {newlevel = newlevel < level.get(v) ? newlevel : level.get(v);}

	    } //if (flow.get(e)<capacity.get(e))

	  } //for(OutEdgeIt e=G.first_OutEdge(w); e.valid(); ++e) 

	  for(InEdgeIt e=G.template first<InEdgeIt>(w); e.valid(); ++e) {

	    NodeIt v=G.tail(e);

	    /*e is the Edge vw.*/

	    if (excess.get(w)==0) break;

	    /*It may happen, that w became inactive in the first for cycle.*/		

	    if(flow.get(e)>0) {             

	      /*e is an Edge of the residual graph */

	      if(level.get(w)==level.get(v)+1) {  

		/*Push is allowed now*/

		if (flow.get(e) > excess.get(w)) { 

		  /*A nonsaturating push.*/

		  if (excess.get(v)==0 && v != s) stack[level.get(v)].push(v); 

		  /*v becomes active.*/

		  flow.set(e, flow.get(e)-excess.get(w));

		  excess.set(v, excess.get(v)+excess.get(w));

		  excess.set(w,0);

		  //std::cout << v << " " << w << " vissza elen nonsat pump "     << std::endl;

		  break; 

		} else {                                               

		  /*A saturating push.*/

		  if (excess.get(v)==0 && v != s) stack[level.get(v)].push(v); 

		  /*v becomes active.*/

		  excess.set(v, excess.get(v)+flow.get(e));

		  excess.set(w, excess.get(w)-flow.get(e));

		  flow.set(e,0);

		  //std::cout << v <<" " << w << " vissza elen sat pump "     << std::endl;

		  if (excess.get(w)==0) { break;}

		} //if (flow.get(e) > excess.get(v)) 

	      } //if(level.get(w)==level.get(v)+1)

	      else {newlevel = newlevel < level.get(v) ? newlevel : level.get(v);}

	    } //if (flow.get(e)>0)

	  } //for

	  if (excess.get(w)>0) {

	    level.set(w,++newlevel);

	    stack[newlevel].push(w);

	    b=newlevel;

	    //std::cout << "The new level of " << w << " is "<< newlevel <<std::endl; 

	  }

	} //else

      } //while(b)

      value = excess.get(t);

      /*Max flow value.*/

    } //void run()

    /*

      Returns the maximum value of a flow.

     */

    T maxflow() {

      return value;

    }

    /*

      For the maximum flow x found by the algorithm, it returns the flow value on Edge e, i.e. x(e). 

    */

    T flowonEdge(EdgeIt e) {

      return flow.get(e);

    }

    /*

      Returns the maximum flow x found by the algorithm.

    */

    typename Graph::EdgeMap<T> allflow() {

      return flow;

    }

    /*

      Returns a minimum cut by using a reverse bfs from t in the residual graph.

    */

    typename Graph::NodeMap<bool> mincut() {

      std::queue<NodeIt> queue;

      mincutvector.set(t,false);      

      queue.push(t);

      while (!queue.empty()) {

        NodeIt w=queue.front();

	queue.pop();

	for(InEdgeIt e=G.template first<InEdgeIt>(w) ; e.valid(); ++e) {

	  NodeIt v=G.tail(e);

	  if (mincutvector.get(v) && flow.get(e) < capacity.get(e) ) {

	    queue.push(v);

	    mincutvector.set(v, false);

	  }

	} // for

	for(OutEdgeIt e=G.template first<OutEdgeIt>(w) ; e.valid(); ++e) {

	  NodeIt v=G.head(e);

	  if (mincutvector.get(v) && flow.get(e) > 0 ) {

	    queue.push(v);

	    mincutvector.set(v, false);

	  }

	} // for

      }

      return mincutvector;

    }

  };

}//namespace marci

#endif