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Cod sursa(job #1990252)

Utilizator oldatlantianSerban Cercelescu oldatlantian Data 11 iunie 2017 03:34:37
Problema Flux maxim Scor 100
Compilator cpp Status done
Runda Arhiva educationala Marime 1.24 kb
#include <bits/stdc++.h>
using namespace std;

const int N = 1024;

int n, m, src, snk, flow;

vector<int> g[N];
int cap[N][N], flw[N][N], lvl[N], far[N], gws[N];

bool bfs() {
    static int it = 0; ++it;
    deque<int> dq({src});
    int u;

    gws[src] = it;
    lvl[src] = 1;

    while (!dq.empty()) {
        u = dq.front();
        dq.pop_front();

        for (auto v: g[u]) if (gws[v] != it && cap[u][v] - flw[u][v] > 0) {
            dq.push_back(v);
            lvl[v] = lvl[u] + 1;
            gws[v] = it; } }

    return (gws[snk] == it); }

int dfs(int u, int mn) {
    if (u == snk) return mn;

    int pump, s(0);
    for (auto v: g[u]) if (lvl[u] + 1 == lvl[v]) {
        pump = dfs(v, min(mn, cap[u][v] - flw[u][v]));

        flw[u][v]+= pump;
        flw[v][u]-= pump;
        mn-= pump;
        s+= pump; }

    return s; }

void dinic() {
    src = 1;
    snk = n;

    while (bfs())
        flow+= dfs(src, 2e9); }

int main() {
    freopen("maxflow.in", "r", stdin);
    freopen("maxflow.out", "w", stdout);
    int u, v, c;

    scanf("%d%d", &n, &m);
    while (m--) {
        scanf("%d%d%d", &u, &v, &c);
        g[u].push_back(v);
        g[v].push_back(u);
        cap[u][v] = c; }

    dinic();

    printf("%d\n", flow);

    return 0; }