src/jiangly/graph/07A-Min-Cost-Flow.hpp
Code
/** 费用流（MCFGraph 旧版）
* 2022-12-12: https://codeforces.com/contest/1766/submission/184974697
*
* 下方为最小费用**最大流**模板，如需求解最小费用**可行流**，需要去除建边限制
**/
struct MCFGraph {
struct Edge {
int v, c, f;
Edge(int v, int c, int f) : v(v), c(c), f(f) {}
};
const int n;
std::vector<Edge> e;
std::vector<std::vector<int>> g;
std::vector<i64> h, dis;
std::vector<int> pre;
bool dijkstra(int s, int t) {
dis.assign(n, std::numeric_limits<i64>::max());
pre.assign(n, -1);
std::priority_queue<std::pair<i64, int>, std::vector<std::pair<i64, int>>, std::greater<std::pair<i64, int>>> que;
dis[s] = 0;
que.emplace(0, s);
while (!que.empty()) {
i64 d = que.top().first;
int u = que.top().second;
que.pop();
if (dis[u] < d) continue;
for (int i : g[u]) {
int v = e[i].v;
int c = e[i].c;
int f = e[i].f;
if (c > 0 && dis[v] > d + h[u] - h[v] + f) {
dis[v] = d + h[u] - h[v] + f;
pre[v] = i;
que.emplace(dis[v], v);
}
}
}
return dis[t] != std::numeric_limits<i64>::max();
}
MCFGraph(int n) : n(n), g(n) {}
void addEdge(int u, int v, int c, int f) {
// if (f < 0) {
g[u].push_back(e.size());
e.emplace_back(v, 0, f);
g[v].push_back(e.size());
e.emplace_back(u, c, -f);
// } else {
// g[u].push_back(e.size());
// e.emplace_back(v, c, f);
// g[v].push_back(e.size());
// e.emplace_back(u, 0, -f);
// }
}
std::pair<int, i64> flow(int s, int t) {
int flow = 0;
i64 cost = 0;
h.assign(n, 0);
while (dijkstra(s, t)) {
for (int i = 0; i < n; ++i) h[i] += dis[i];
int aug = std::numeric_limits<int>::max();
for (int i = t; i != s; i = e[pre[i] ^ 1].v) aug = std::min(aug, e[pre[i]].c);
for (int i = t; i != s; i = e[pre[i] ^ 1].v) {
e[pre[i]].c -= aug;
e[pre[i] ^ 1].c += aug;
}
flow += aug;
cost += i64(aug) * h[t];
}
return std::make_pair(flow, cost);
}
};
#line 1 "src/jiangly/graph/07A-Min-Cost-Flow.hpp"
/** 费用流（MCFGraph 旧版）
* 2022-12-12: https://codeforces.com/contest/1766/submission/184974697
*
* 下方为最小费用**最大流**模板，如需求解最小费用**可行流**，需要去除建边限制
**/
struct MCFGraph {
struct Edge {
int v, c, f;
Edge(int v, int c, int f) : v(v), c(c), f(f) {}
};
const int n;
std::vector<Edge> e;
std::vector<std::vector<int>> g;
std::vector<i64> h, dis;
std::vector<int> pre;
bool dijkstra(int s, int t) {
dis.assign(n, std::numeric_limits<i64>::max());
pre.assign(n, -1);
std::priority_queue<std::pair<i64, int>, std::vector<std::pair<i64, int>>, std::greater<std::pair<i64, int>>> que;
dis[s] = 0;
que.emplace(0, s);
while (!que.empty()) {
i64 d = que.top().first;
int u = que.top().second;
que.pop();
if (dis[u] < d) continue;
for (int i : g[u]) {
int v = e[i].v;
int c = e[i].c;
int f = e[i].f;
if (c > 0 && dis[v] > d + h[u] - h[v] + f) {
dis[v] = d + h[u] - h[v] + f;
pre[v] = i;
que.emplace(dis[v], v);
}
}
}
return dis[t] != std::numeric_limits<i64>::max();
}
MCFGraph(int n) : n(n), g(n) {}
void addEdge(int u, int v, int c, int f) {
// if (f < 0) {
g[u].push_back(e.size());
e.emplace_back(v, 0, f);
g[v].push_back(e.size());
e.emplace_back(u, c, -f);
// } else {
// g[u].push_back(e.size());
// e.emplace_back(v, c, f);
// g[v].push_back(e.size());
// e.emplace_back(u, 0, -f);
// }
}
std::pair<int, i64> flow(int s, int t) {
int flow = 0;
i64 cost = 0;
h.assign(n, 0);
while (dijkstra(s, t)) {
for (int i = 0; i < n; ++i) h[i] += dis[i];
int aug = std::numeric_limits<int>::max();
for (int i = t; i != s; i = e[pre[i] ^ 1].v) aug = std::min(aug, e[pre[i]].c);
for (int i = t; i != s; i = e[pre[i] ^ 1].v) {
e[pre[i]].c -= aug;
e[pre[i] ^ 1].c += aug;
}
flow += aug;
cost += i64(aug) * h[t];
}
return std::make_pair(flow, cost);
}
};
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