Cod sursa(job #2977602)

Utilizator JustinTrudeauBarack Obama JustinTrudeau Data 11 februarie 2023 22:47:27
Problema Flux maxim Scor 100
Compilator cpp-64 Status done
Runda Arhiva educationala Marime 2.46 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 <queue>
#include <unordered_map>
#include <unordered_set>
#include <iomanip>
#include <cassert>
#include <bitset>
#include <sstream>
#include <chrono>
#include <cstring>
#include <numeric>

using namespace std;

const int INF = (int)1e9 + 7;

struct Edge {
	int to;
	int cap;
};

struct Flow {
	int n;
	vector<Edge> edges;
	vector<vector<int>> g;
	vector<int> level;
	vector<int> pos;

	void init(int nn) {
		n = nn;
		edges.clear();
		g.clear();
		g.resize(n);
		level.clear();
		level.resize(n);
		pos.resize(n);
	}

	void add(int a, int b, int c) {
		a--;
		b--;
		assert(0 <= a && a < n);
		assert(0 <= b && b < n);
		edges.push_back({ b, c });
		edges.push_back({ a, 0 });
		g[a].push_back((int)edges.size() - 2);
		g[b].push_back((int)edges.size() - 1);
	}

	bool bfs() {
		for (int i = 0; i < n; i++) level[i] = -1;
		queue<int> q;
		q.push(0);
		level[0] = 0;
		while (!q.empty()) {
			int a = q.front();
			q.pop();
			for (auto& i : g[a]) {
				int b = edges[i].to;
				int cap = edges[i].cap;
				if (cap && level[b] == -1) {
					level[b] = 1 + level[a];
					q.push(b);
				}
			}
		}
		return level[n - 1] != -1;
	}

	int dfs(int a, int cur) {
		if (a == n - 1 || cur == 0) return cur;
		while (pos[a] < (int)g[a].size()) {
			int i = g[a][pos[a]++];
			if (edges[i].cap > 0 && level[edges[i].to] == 1 + level[a]) {
				int c = dfs(edges[i].to, min(cur, edges[i].cap));
				if (c) {
					edges[i].cap -= c;
					edges[i ^ 1].cap += c;
					pos[a]--;
					return c;
				}
			}
		}
		return 0;
	}

	int pump() {
		int sol = 0;
		while (bfs()) {
			for (int i = 0; i < n; i++) pos[i] = 0;
			int x = 0;
			while (1) {
				x = dfs(0, INF);
				sol += x;
				if (!x) break;
			}
		}
		return sol;
	}
};

signed main() {
#ifdef INFOARENA
	ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);
	freopen("maxflow.in", "r", stdin);
	freopen("maxflow.out", "w", stdout);
#else
	FILE* stream;
	freopen_s(&stream, "input.txt", "r", stdin);
#endif

	int n, m;
	cin >> n >> m;
	Flow f;
	f.init(n);
	for (int i = 1; i <= m; i++) {
		int a, b, c;
		cin >> a >> b >> c;
		f.add(a, b, c);
	}
	cout << f.pump() << "\n";

	return 0;
}