Cod sursa(job #1365933)

Utilizator CosminRusuCosmin Rusu CosminRusu Data 28 februarie 2015 17:01:24
Problema Flux maxim Scor 100
Compilator cpp Status done
Runda Arhiva educationala Marime 1.71 kb
#include <iostream>
#include <fstream>
#include <bitset>
#include <queue>
#include <vector>

using namespace std;

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

const int maxn = 1005;
const int oo = 0x3f3f3f3f;

int n, m, c[maxn][maxn], father[maxn];
vector <int> g[maxn];
queue <int> q;
bitset <maxn> used;

inline bool bfs(int source, int sink) {
    used.reset();
    q.push(source);
    used[source] = 1;
    while(!q.empty()) {
        int node = q.front();
        q.pop();
        if(node == sink)
            continue;
        for(vector <int> :: iterator it = g[node].begin() ; it != g[node].end() ; ++ it)
            if(!used[*it] && c[node][*it] > 0) {
                used[*it] = 1;
                father[*it] = node;
                q.push(*it);
            }
    }
    return used[sink];
}

inline int getmaxflow(int source, int sink) {
    int maxflow = 0;
    while(bfs(source, sink))
        for(vector <int> :: iterator it = g[sink].begin() ; it != g[sink].end() ; ++ it) {
            if(!used[*it] || c[*it][sink] <= 0)
                continue;
            father[sink] = *it;
            int bottleneck = oo;
            for(int i = sink ; i != source ; i = father[i])
                bottleneck = min(bottleneck, c[father[i]][i]);
            for(int i = sink ; i != source ; i = father[i]) {
                c[father[i]][i] -= bottleneck;
                c[i][father[i]] += bottleneck;
            }
            maxflow += bottleneck;
        }
    return maxflow;
}

int main() {
    fin >> n >> m;
    for(int i = 1 ; i <= m ; ++ i) {
        int x, y, z;
        fin >> x >> y >> z;
        g[x].push_back(y);
        g[y].push_back(x);
        c[x][y] = z;
    }
    fout << getmaxflow(1, n) << '\n';
}