77 lines
2.3 KiB
Rust
77 lines
2.3 KiB
Rust
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// loj-101.rs
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use std::collections::VecDeque;
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#[derive(Clone, Debug)]
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struct Edge {
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to: usize,
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cap: i64,
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flow: i64,
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rev: (usize, usize)
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}
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struct Net(Vec<Vec<Edge>>);
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impl Net {
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fn new(n: usize) -> Self {
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Self(vec![vec![];n+1])
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}
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fn add_edge(&mut self, from: usize, to: usize, cap: i64) {
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let to_edge = Edge {to, cap, flow: 0, rev: (to, self.0[to].len())};
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self.0[from].push(to_edge);
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let from_edge = Edge {to: from, cap: 0, flow: 0, rev: (from, self.0[from].len() - 1)};
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self.0[to].push(from_edge);
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}
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fn max_flow(&mut self, s: usize, t: usize) -> i64 {
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let n = self.0.len();
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let mut pa = vec![(0, 0);n+1];
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let mut res = 0;
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loop {
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let mut pf = vec![0;n+1];
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let mut dq = VecDeque::new();
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dq.push_back(s);
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pf[s] = i64::MAX;
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while let Some(v) = dq.pop_front() {
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for (i, ne) in self.0[v].iter().enumerate() {
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if pf[ne.to] == 0 && ne.cap > ne.flow {
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pf[ne.to] = pf[v].min(ne.cap - ne.flow);
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pa[ne.to] = (v, i);
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dq.push_back(ne.to);
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}
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}
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if pf[t] != 0 {
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break;
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}
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}
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if pf[t] == 0 {
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break;
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}
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let mut p = t;
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while pa[p].0 != 0 {
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let (x, y) = pa[p];
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self.0[x][y].flow += pf[t];
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let (z, w) = self.0[x][y].rev;
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self.0[z][w].flow -= pf[t];
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p = x;
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}
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res += pf[t];
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}
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res
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}
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}
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fn main() {
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let mut buf = String::new();
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std::io::stdin().read_line(&mut buf).ok();
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let tmp: Vec<usize> = buf.trim().split(' ').map(|x|x.parse::<usize>().unwrap()).collect::<Vec<usize>>();
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let (n, m, s, t) = (tmp[0], tmp[1], tmp[2], tmp[3]);
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let mut net = Net::new(n);
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for _ in 0..m {
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buf.clear();
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std::io::stdin().read_line(&mut buf).ok();
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let tmp: Vec<i64> = buf.trim().split(' ').map(|x|x.parse::<i64>().unwrap()).collect::<Vec<i64>>();
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net.add_edge(tmp[0] as usize, tmp[1] as usize, tmp[2]);
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}
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println!("{}", net.max_flow(s, t));
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}
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