src/jiangly/graph/06B-Max-Flow.hpp
Code
/** 最大流（Flow 旧版其二，浮点数应用）
* 2022-04-09: https://cf.dianhsu.com/gym/104288/submission/201412765
**/
template<class T>
struct Flow {
const int n;
struct Edge {
int to;
T cap;
Edge(int to, T cap) : to(to), cap(cap) {}
};
std::vector<Edge> e;
std::vector<std::vector<int>> g;
std::vector<int> cur, h;
Flow(int n) : n(n), g(n) {}
bool bfs(int s, int t) {
h.assign(n, -1);
std::queue<int> que;
h[s] = 0;
que.push(s);
while (!que.empty()) {
const int u = que.front();
que.pop();
for (int i : g[u]) {
auto [v, c] = e[i];
if (c > 0 && h[v] == -1) {
h[v] = h[u] + 1;
if (v == t) {
return true;
}
que.push(v);
}
}
}
return false;
}
T dfs(int u, int t, T f) {
if (u == t) {
return f;
}
auto r = f;
double res = 0;
for (int &i = cur[u]; i < int(g[u].size()); ++i) {
const int j = g[u][i];
auto [v, c] = e[j];
if (c > 0 && h[v] == h[u] + 1) {
auto a = dfs(v, t, std::min(r, c));
res += a;
e[j].cap -= a;
e[j ^ 1].cap += a;
r -= a;
if (r == 0) {
return f;
}
}
}
return res;
}
void addEdge(int u, int v, T c) {
g[u].push_back(e.size());
e.emplace_back(v, c);
g[v].push_back(e.size());
e.emplace_back(u, 0);
}
T maxFlow(int s, int t) {
T ans = 0;
while (bfs(s, t)) {
cur.assign(n, 0);
ans += dfs(s, t, 1E100);
}
return ans;
}
};
#line 1 "src/jiangly/graph/06B-Max-Flow.hpp"
/** 最大流（Flow 旧版其二，浮点数应用）
* 2022-04-09: https://cf.dianhsu.com/gym/104288/submission/201412765
**/
template<class T>
struct Flow {
const int n;
struct Edge {
int to;
T cap;
Edge(int to, T cap) : to(to), cap(cap) {}
};
std::vector<Edge> e;
std::vector<std::vector<int>> g;
std::vector<int> cur, h;
Flow(int n) : n(n), g(n) {}
bool bfs(int s, int t) {
h.assign(n, -1);
std::queue<int> que;
h[s] = 0;
que.push(s);
while (!que.empty()) {
const int u = que.front();
que.pop();
for (int i : g[u]) {
auto [v, c] = e[i];
if (c > 0 && h[v] == -1) {
h[v] = h[u] + 1;
if (v == t) {
return true;
}
que.push(v);
}
}
}
return false;
}
T dfs(int u, int t, T f) {
if (u == t) {
return f;
}
auto r = f;
double res = 0;
for (int &i = cur[u]; i < int(g[u].size()); ++i) {
const int j = g[u][i];
auto [v, c] = e[j];
if (c > 0 && h[v] == h[u] + 1) {
auto a = dfs(v, t, std::min(r, c));
res += a;
e[j].cap -= a;
e[j ^ 1].cap += a;
r -= a;
if (r == 0) {
return f;
}
}
}
return res;
}
void addEdge(int u, int v, T c) {
g[u].push_back(e.size());
e.emplace_back(v, c);
g[v].push_back(e.size());
e.emplace_back(u, 0);
}
T maxFlow(int s, int t) {
T ans = 0;
while (bfs(s, t)) {
cur.assign(n, 0);
ans += dfs(s, t, 1E100);
}
return ans;
}
};
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