Cod sursa(job #1641672)

Utilizator howsiweiHow Si Wei howsiwei Data 9 martie 2016 09:37:39
Problema Flux maxim Scor 100
Compilator cpp Status done
Runda Arhiva educationala Marime 1.43 kb
#include <iostream>
#include <cstdio>
#include <vector>
#include <queue>
using namespace std;
const int oo = 0x1f1f1f1f;
int n, m, s, t;
vector<vector<int>> al;
vector<vector<int>::iterator> cur;
vector<int> el;
vector<int> cl;
vector<int> d;

void addedge1(int u, int v, int c) {
	al[u].push_back(el.size());
	el.push_back(v);
	cl.push_back(c);
}

void addedge(int u, int v, int c) {
	addedge1(u, v, c);
	addedge1(v, u, 0);
}

int dfs(int u, int c0) {
	if (u == t) return c0;
	int c = c0;
	for (; cur[u] != al[u].end(); ++cur[u]) {
		int i = *cur[u];
		if (!(d[u] > d[el[i]] && cl[i] > 0)) continue;
		int f = dfs(el[i], min(c, cl[i]));
		c -= f;
		cl[i] -= f;
		cl[i^1] += f;
		if (c == 0) break;
	}
	if (c > 0) d[u] = n;
	return c0-c;
}

void solve() {
	cin >> n >> m;
	s = 0, t = n-1;
	al.assign(n, {});
	cur.resize(n);
	el.clear();
	cl.clear();
	for (int i = 0; i < m; i++) {
		int u, v, c;
		cin >> u >> v >> c;
		u--, v--;
		addedge(u, v, c);
	}
	int mf = 0;
	while (true) {
		d.assign(n, n);
		d[t] = 0;
		queue<int> q;
		q.push(t);
		do {
			int v = q.front();
			q.pop();
			cur[v] = al[v].begin();
			for (int i: al[v]) if (d[el[i]] == n && cl[i^1] > 0) {
				d[el[i]] = d[v]+1;
				q.push(el[i]);
			}
		} while (!q.empty());
		if (d[s] == n) break;
		mf += dfs(s, oo);
	}
	printf("%d\n", mf);
}

int main() {
#ifdef INFOARENA
	freopen("maxflow.in", "r", stdin);
	freopen("maxflow.out", "w", stdout);
#endif
	cin.sync_with_stdio(false);
	solve();
}