Cod sursa(job #1048917)

Utilizator RobertSSamoilescu Robert RobertS Data 6 decembrie 2013 17:17:43
Problema Flux maxim Scor 70
Compilator cpp Status done
Runda Arhiva educationala Marime 1.71 kb
#include<iostream>
#include<fstream>
#include<cstring>
#include<queue>
#include<vector>
using namespace std;
#define MAX_N 1000
#define mp make_pair 
#define pb push_back

int n, m;

ifstream fin("maxflow.in");
ofstream fout("maxflow.out");

int graph[MAX_N][MAX_N];
vector<int> list[MAX_N];

void read(){
	fin >> n >> m;
	
	int a, b, c;
	for(int i=1; i<=m; i++){
		fin >> a >> b >> c;
		graph[a][b] = c;
		list[a].push_back(b);
	}	
}

int father[MAX_N]; // vector de tati folosit in parcurgerea bf;
queue<int> coada; // coada in care adaug pe rand nodurile in parcurgerea bf

bool bf(int s, int t){ // s - pct de plecare, t-pct destinatie
	bool viz[MAX_N];
	for(int i=1; i<=n; i++)	viz[i] = false;
	
	coada.push(s);
	father[s] = -1; // sursa nu are tata;
	viz[s] = true;
	
	while(!coada.empty()){
		
		int nod = coada.front();
		coada.pop();
		
		for(size_t i=0; i<list[nod].size(); i++){
			int next = list[nod][i];
			if(!viz[next] && graph[nod][next]){
				viz[next] = true;
				father[next] = nod;
				coada.push(next);
			}
		}
	
	}
	
	return viz[t] == true;

} // functia returneaza true daca exista drum de la s la t;

int  solve(int s, int t){
	int max_flow = 0;
	while(bf(s,t)){ // cat timp exista drum de la s la t;
		int minim = graph[father[t]][t];
		for(int i=father[t]; i!=s; i=father[i]){
			int new_min  = graph[father[i]][i];
			if(minim > new_min) minim = new_min;
		}
		
		for(int i=t; i!=s; i=father[i]){
			if(graph[i][father[i]] == 0) list[i].push_back(father[i]);
			graph[i][father[i]] += minim;
			graph[father[i]][i] -= minim;
		}
		max_flow +=minim;
	}

	return max_flow;
}


int main(){
	read();
	
	fout << solve(1,n);
return 0;
}