Cod sursa(job #2237659)

Utilizator caesar2001Stoica Alexandru caesar2001 Data 2 septembrie 2018 16:06:25
Problema Flux maxim Scor 100
Compilator cpp Status done
Runda Arhiva educationala Marime 2.12 kb
#include <bits/stdc++.h>

using namespace std;
ifstream in("maxflow.in");
ofstream out("maxflow.out");

const int NMAX = 1005;

struct Edge {
    int to, cap, flow, rev;
};

vector<Edge> g[NMAX];
int dist[NMAX], src, dest, c[NMAX][NMAX], rem[NMAX], n, m;

void addEdge(int i, int j) {
    Edge a = {j, c[i][j], 0, g[j].size()};
    Edge b = {i, c[j][i], 0, g[i].size()};
    g[i].push_back(a);
    g[j].push_back(b);
}

bool bfs() {
    for(int i = 1; i <= n; i ++)
        dist[i] = -1;

    queue<int> q;
    dist[src] = 0;
    q.push(src);

    while(q.size()) {
        int from = q.front();
        q.pop();
        for(auto it : g[from]) {
            if(dist[it.to] == -1 && it.cap > it.flow) {
                dist[it.to] = 1 + dist[from];
                q.push(it.to);
            }
        }
    }
    return (0 <= dist[dest]);
}

int dfs(int from, int deltaflow) {
    if(from == dest)
        return deltaflow;
    for(int i = rem[from]; i < g[from].size(); i ++) {
        Edge &e = g[from][i];
        if(dist[e.to] == dist[from] + 1) {
            int addflow = dfs(e.to, min(deltaflow, e.cap - e.flow));
            if(addflow > 0) {
                Edge &rev = g[e.to][e.rev];
                e.flow += addflow;
                rev.flow -= addflow;
                rem[from] = i;
                return addflow;
            }
        }
    }
    return 0;
}

int dinic() {
    int maxflow = 0;
    while(bfs()) {
        for(int i = 1; i <= n; i ++)
            rem[i] = 0;
        int aux = dfs(src, INT_MAX);
        while(aux) {
            maxflow += aux;
            aux = dfs(src, INT_MAX);
        }
    }
    return maxflow;
}

int main() {
    ios::sync_with_stdio(false);
    in.tie(NULL);
    out.tie(NULL);

    in >> n >> m;
    src = 1;
    dest = n;
    for(int i = 1; i <= m; i ++) {
        int x, y, z;
        in >> x >> y >> z;
        c[x][y] = z;
    }
    for(int i = 1; i <= n; i ++)
        for(int j = i + 1; j <= n; j ++)
            if(c[i][j] || c[j][i])
                addEdge(i, j);

    out << dinic();

    return 0;
}