Create edmonds-karp.rs

graph/edmonds-karp.rs

@@ -0,0 +1,76 @@
+// loj-101.rs
+
+use std::collections::VecDeque;
+
+#[derive(Clone, Debug)]
+struct Edge {
+    to: usize,
+    cap: i64,
+    flow: i64,
+    rev: (usize, usize)
+}
+
+struct Net(Vec<Vec<Edge>>);
+
+impl Net {
+    fn new(n: usize) -> Self {
+        Self(vec![vec![];n+1])
+    }
+    fn add_edge(&mut self, from: usize, to: usize, cap: i64) {
+        let to_edge = Edge {to, cap, flow: 0, rev: (to, self.0[to].len())};
+        self.0[from].push(to_edge);
+        let from_edge = Edge {to: from, cap: 0, flow: 0, rev: (from, self.0[from].len() - 1)};
+        self.0[to].push(from_edge);
+    }
+    fn max_flow(&mut self, s: usize, t: usize) -> i64 {
+        let n = self.0.len();
+        let mut pa = vec![(0, 0);n+1];
+        let mut res = 0;
+        loop {
+            let mut pf = vec![0;n+1];
+            let mut dq = VecDeque::new();
+            dq.push_back(s);
+            pf[s] = i64::MAX;
+            while let Some(v) = dq.pop_front() {
+                for (i, ne) in self.0[v].iter().enumerate() {
+                    if pf[ne.to] == 0 && ne.cap > ne.flow {
+                        pf[ne.to] = pf[v].min(ne.cap - ne.flow);
+                        pa[ne.to] = (v, i);
+                        dq.push_back(ne.to);
+                    }
+                }
+                if pf[t] != 0 {
+                    break;
+                }
+            }
+            if pf[t] == 0 {
+                break;
+            }
+            let mut p = t;
+            while pa[p].0 != 0 {
+                let (x, y) = pa[p];
+                self.0[x][y].flow += pf[t];
+                let (z, w) = self.0[x][y].rev;
+                self.0[z][w].flow -= pf[t];
+                p = x;
+            }
+            res += pf[t];
+        }
+        res
+    }
+}
+
+fn main() {
+    let mut buf = String::new();
+    std::io::stdin().read_line(&mut buf).ok();
+    let tmp: Vec<usize> = buf.trim().split(' ').map(|x|x.parse::<usize>().unwrap()).collect::<Vec<usize>>();
+    let (n, m, s, t) = (tmp[0], tmp[1], tmp[2], tmp[3]);
+    let mut net = Net::new(n);
+    for _ in 0..m {
+        buf.clear();
+        std::io::stdin().read_line(&mut buf).ok();
+        let tmp: Vec<i64> = buf.trim().split(' ').map(|x|x.parse::<i64>().unwrap()).collect::<Vec<i64>>();
+        net.add_edge(tmp[0] as usize, tmp[1] as usize, tmp[2]);
+    }
+    println!("{}", net.max_flow(s, t));
+}