HDU 1532 Drainage Ditches——最大流EK算法

模板题

#include <cstdio>
#include <cstring>
#include <iostream>
#include <algorithm>
#include <vector>

using namespace std;

const int INF = 0x3f3f3f3f;
const int maxn = 1000 + 10;

struct Node {
int to;
int cap;
int rev;
};

vector<Node> v[maxn];
bool used[maxn];

void add_node(int from, int to, int cap) {
v[from].push_back((Node){to, cap, v[to].size()});
v[to].push_back((Node){from, 0, v[from].size() - 1});
}

int dfs(int s, int t, int f) {
if (s == t) return f;
used[s] = true;
for (int i = 0; i < v[s].size(); i++) {
Node &temp = v[s][i];
if (used[temp.to] == false && temp.cap > 0) {
int d = dfs(temp.to, t, min(f, temp.cap));
if (d > 0) {
temp.cap -= d;
v[temp.to][temp.rev].cap += d;
return d;
}
}
}
return 0;
}

int max_flow(int s, int t) {
int flow = 0;
while (true) {
memset(used, false, sizeof(used));
int f = dfs(s, t, INF);
if (f == 0) return flow;
flow += f;
}
}

int main()
{
int n, m;
while (scanf("%d %d", &n, &m) == 2) {
memset(v, 0, sizeof(v));
for (int i = 0; i < n; i++) {
int x, y, z;
scanf("%d %d %d", &x, &y, &z);
add_node(x, y, z);
}
printf("%d\n", max_flow(1, m));
}
return 0;
}