Cod sursa(job #3121644)

Utilizator FunnyStockyMihnea Andreescu FunnyStocky Data 14 aprilie 2023 16:22:57
Problema Flux maxim Scor 0
Compilator cpp-64 Status done
Runda Arhiva educationala Marime 2.39 kb
#include <cmath>
#include <functional>
#include <fstream>
#include <iostream>
#include <vector>
#include <algorithm>
#include <string>
#include <set>
#include <map>
#include <list>
#include <time.h>
#include <math.h>
#include <random>
#include <deque>
#include <cassert>
#include <queue>
#include <unordered_map>
#include <unordered_set>
#include <iomanip>
#include <bitset>
#include <sstream>
#include <stack>
#include <chrono>
#include <cstring>
#include <numeric>
using namespace std;
struct F {
	const int INF = (int)1e9 + 7;
	int n;
	int flow;
	struct E {
		int to, cap;
	};
	vector<E> es;
	vector<int> l;
	vector<int> ptr;
	vector<vector<int>> g;
	vector<int> q;
	F(int nn) :
		n(nn),
		l(nn),
		ptr(nn),
		g(nn),
		flow(0) {
		
	};
	void add(int a, int b, int c) {
		a--;
		b--;
		assert(0 <= a && a < n);
		assert(0 <= b && b < n);
		es.push_back({ b, c });
		es.push_back({ a, 0 });
		g[a].push_back((int)es.size() - 2);
		g[b].push_back((int)es.size() - 1);
	}
	bool bfs() {
		for (int i = 0; i < n; i++) {
			l[i] = -1;
		}
		l[0] = 0;
		q.clear();
		q.push_back(0);
		for (int it = 0; it < (int)q.size(); it++) {
			int a = q[it];
			for (auto& i : g[a]) {
				if (es[i].cap) {
					int b = es[i].to;
					if (l[b] == -1) {
						l[b] = 1 + l[a];
						q.push_back(b);
					}
				}
			}
		}
		return l[n - 1] != -1;
	}
	int dfs(int a, int cap) {
		if (a == n - 1 || cap == 0) {
			return cap;
		}
		while (ptr[a] < (int)g[a].size()) {
			int i = g[a][ptr[a]++];
			if (es[i].cap) {
				int b = es[i].to;
				if (l[b] == 1 + l[a]) {
					int r = dfs(b, min(cap, es[i].cap));
					if (r) {
						es[i].cap -= r;
						es[i ^ 1].cap += r;
						ptr[a]--;
						return r;
					}
				}
			}
		}
		return 0;
	}
	void pump() {
		while (bfs()) {
			for (int i = 0; i < n; i++) {
				ptr[i] = 0;
			}
			int what;
			do {
				what = dfs(0, INF);
				flow += what;
			} while (what > 0);
		}
	}
};
signed main() {
#ifndef ONLINE_JUDGE
	FILE* stream;
	freopen_s(&stream, "input.txt", "r", stdin);
#else
	ios::sync_with_stdio(false);
	cin.tie(0); cout.tie(0);
	freopen("maxflow.in", "r", stdin);
	freopen("maxflow.out", "w", stdout);
#endif
	int n, m;
	cin >> n >> m;
	F f(n);
	for (int i = 1; i <= m; i++) {
		int a, b, c;
		cin >> a >> b >> c;
		f.add(a, b, c);
	}
	f.pump();
	cout << f.flow << "\n";
	return 0;
}