Create dinic.rs

graph/dinic.rs

@@ -0,0 +1,82 @@
+// loj-101.rs
+
+use std::collections::VecDeque;
+
+#[derive(Clone, Copy, Debug)]
+struct Edge {
+    to: usize,
+    flow: i64,
+    cap: i64,
+    rev: usize,
+}
+
+struct Net(Vec<Vec<Edge>>, Vec<usize>, Vec<bool>);
+
+impl Net {
+    fn new(n: usize) -> Self {
+        Self(vec![vec![]; n+1], vec![0; n+1], vec![false; n+1])
+    }
+    fn add_edge(&mut self, from: usize, to: usize, cap: i64) {
+        let to_edge = Edge {to, cap, flow: 0, rev: self.0[to].len()};
+        self.0[from].push(to_edge);
+        let from_edge = Edge {to: from, flow: 0, cap: 0, rev: self.0[from].len() - 1};
+        self.0[to].push(from_edge);
+    }
+    fn bfs(&mut self, s: usize, t: usize) -> bool {
+        self.1.fill(0);
+        let mut dq = VecDeque::new();
+        self.1[s] = 1;
+        dq.push_back((s, 1));
+        while let Some((v, l)) = dq.pop_front() {
+            for e in &self.0[v] {
+                if self.1[e.to] == 0 && e.cap > e.flow {
+                    self.1[e.to] = l + 1;
+                    dq.push_back((e.to, l + 1));
+                }
+            }
+        }
+        self.1[t] != 0
+    }
+    fn dfs(&mut self, s: usize, t: usize, cap: i64) -> i64 {
+        if self.2[s] { return 0; }
+        self.2[s] = true;
+        if s == t { return cap; }
+        let mut res = 0;
+        let n = self.0[s].len();
+        for i in 0..n {
+            let e = self.0[s][i];
+            if e.cap > e.flow && self.1[e.to] == self.1[s] + 1 {
+                let new = self.dfs(e.to, t, (cap - res).min(e.cap - e.flow));
+                self.0[s][i].flow += new;
+                self.0[e.to][e.rev].flow -= new;
+                res += new;
+                if res == cap { return res; }
+            }
+        }
+        res
+    }
+    fn max_flow(&mut self, s: usize, t: usize) -> i64 {
+        let mut res = 0;
+        while self.bfs(s, t) {
+            self.2.fill(false);
+            res += self.dfs(s, t, i64::MAX);
+        }
+        res
+    }
+}
+
+fn main() {
+    let mut buf = String::new();
+    std::io::stdin().read_line(&mut buf).ok();
+    let nmst: Vec<usize> = buf.trim().split(' ').map(|x|x.parse::<usize>().unwrap()).collect::<Vec<usize>>();
+    let (n, m, s, t) = (nmst[0], nmst[1], nmst[2], nmst[3]);
+    let mut net = Net::new(n);
+    for _ in 0..m {
+        buf.clear();
+        std::io::stdin().read_line(&mut buf).ok();
+        let uvc: Vec<i64> = buf.trim().split(' ').map(|x|x.parse::<i64>().unwrap()).collect::<Vec<i64>>();
+        let (u, v, c) = (uvc[0] as usize, uvc[1] as usize, uvc[2]);
+        net.add_edge(u, v, c);
+    }
+    println!("{}", net.max_flow(s, t));
+}