Cod sursa(job #1953551)

Utilizator mouse_wirelessMouse Wireless mouse_wireless Data 4 aprilie 2017 21:26:56
Problema Flux maxim Scor 10
Compilator cpp Status done
Runda Arhiva educationala Marime 2.05 kb
#include <cstdio>
#include <climits>
#include <algorithm>
#include <vector>
#include <cstring>
#include <queue>
using namespace std;

#ifdef INFOARENA
#define ProblemName "maxflow"
#endif

#define MCONCAT(A, B) A B
#ifdef ProblemName
#define InFile MCONCAT(ProblemName, ".in")
#define OuFile MCONCAT(ProblemName, ".out")
#else
#define InFile "fis.in"
#define OuFile "fis.out"
#endif
typedef long long LL;

#define MAXN 1100
typedef vector< vector<int> > graph;
graph G;
int N;
int C[MAXN][MAXN], F[MAXN][MAXN];
vector<int>::iterator nedge[MAXN];
int dst[MAXN];
#define INFINIT 0x3F3F3F3F

queue<int> Q;
bool BFS(int s) {
	memset(dst, 0x3F, sizeof(dst));
	dst[s] = 0;
	while (!Q.empty()) Q.pop();
	Q.push(s);
	while (!Q.empty()) {
		int t = Q.front();
		Q.pop();
		for (const auto &u : G[t]) {
			if (F[t][u] >= C[t][u]) continue;
			if(dst[u] != INFINIT) continue;
			dst[u] = dst[t] + 1;
			Q.push(u);
		}
	}
	return (dst[N - 1] != INFINIT);
}

int DFS(int v, int flow) {
	if (v == (N - 1)) return flow;
	for (auto &u = nedge[v]; u != G[v].end(); ++u) {
		if (F[v][*u] >= C[v][*u]) continue;
		if (dst[v] + 1 != dst[*u]) continue;
		int actualFlow = DFS(*u, C[v][*u] - F[v][*u]);
		if (actualFlow == 0) continue;
		if (flow < actualFlow) actualFlow = flow;
		F[v][*u] += actualFlow;
		F[*u][v] -= actualFlow;
		return actualFlow;
	}
	return 0;
}

int blockingFlow() {
	int totalFlow = 0;
	for (int i = 0; i < N; ++i)
		nedge[i] = G[i].begin();
	int flow = 0;
	while (flow = DFS(0, INFINIT)) totalFlow += flow;
	return totalFlow;
}

int Dinic() {
	int flow = 0;
	while (BFS(0)) flow += blockingFlow();
	return flow;
}

void input() {
	int M;
	scanf("%d%d", &N, &M);
	G.resize(N);
	for (int i = 0; i < M; ++i) {
		int a, b, c;
		scanf("%d%d%d", &a, &b, &c);
		--a, --b;
		G[a].push_back(b);
		G[b].push_back(a);
		C[a][b] = c;
		C[b][a] = 0;
		F[a][b] = F[b][a] = 0;
	}
}

int main() {
	freopen(InFile, "r", stdin);
	freopen(OuFile, "w", stdout);
	input();
	printf("%d\n", Dinic());
	return 0;
}