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pub mod dinitz {
const INF: i64 = 1 << 60;
pub struct Edge {
pub to: usize,
pub rev: usize,
pub is_reversed: bool,
pub cap: i64,
}
pub struct Dinitz {
pub g: Vec<Vec<Edge>>,
}
impl Dinitz {
pub fn new(v: usize) -> Dinitz {
let mut g: Vec<Vec<Edge>> = Vec::new();
for _ in 0..v {
g.push(Vec::new());
}
Dinitz { g }
}
pub fn add_edge(&mut self, from: usize, to: usize, cap: i64) {
let to_len = self.g[to].len();
let from_len = self.g[from].len();
self.g[from].push(Edge {
to,
rev: to_len,
is_reversed: false,
cap,
});
self.g[to].push(Edge {
to: from,
rev: from_len,
is_reversed: true,
cap: 0,
});
}
fn dfs(
&mut self,
v: usize,
sink: usize,
flow: i64,
level: &[i32],
iter: &mut [usize],
) -> i64 {
if v == sink {
return flow;
}
while iter[v] < self.g[v].len() {
let flow = std::cmp::min(flow, self.g[v][iter[v]].cap);
let to = self.g[v][iter[v]].to;
if flow > 0 && level[v] < level[to] {
let flowed = self.dfs(to, sink, flow, level, iter);
if flowed > 0 {
let rev = self.g[v][iter[v]].rev;
self.g[v][iter[v]].cap -= flowed;
self.g[to][rev].cap += flowed;
return flowed;
}
}
iter[v] += 1;
}
0
}
fn bfs(&self, s: usize) -> Vec<i32> {
let v = self.g.len();
let mut level = vec![-1; v];
level[s] = 0;
let mut deque = std::collections::VecDeque::new();
deque.push_back(s);
while let Some(v) = deque.pop_front() {
for e in self.g[v].iter() {
if e.cap > 0 && level[e.to] < 0 {
level[e.to] = level[v] + 1;
deque.push_back(e.to);
}
}
}
level
}
pub fn max_flow(&mut self, s: usize, t: usize) -> i64 {
let v = self.g.len();
let mut flow: i64 = 0;
loop {
let level = self.bfs(s);
if level[t] < 0 {
return flow;
}
let mut iter = vec![0; v];
loop {
let f = self.dfs(s, t, INF, &level, &mut iter);
if f == 0 {
break;
}
flow += f;
}
}
}
}
}
#[cfg(test)]
mod tests {
use super::*;
use crate::utils::test_helper::Tester;
#[test]
fn solve_grl_6_a() {
let tester = Tester::new("./assets/GRL_6_A/in/", "./assets/GRL_6_A/out/");
tester.test_solution(|sc| {
let v = sc.read();
let e = sc.read();
let mut dinitz = dinitz::Dinitz::new(v);
for _ in 0..e {
let from = sc.read();
let to = sc.read();
let c = sc.read();
dinitz.add_edge(from, to, c);
}
let flow = dinitz.max_flow(0, v - 1);
sc.write(format!("{}\n", flow));
});
}
}