typical90 039

typical90/src/bin/039.rs

@@ -0,0 +1,34 @@
+use proconio::{input, marker::Usize1};
+
+fn adjacency_list(n: usize, uv: &Vec<(usize, usize)>) -> Vec<Vec<usize>> {
+    let mut e = vec![vec![]; n];
+    for &(u, v) in uv.iter() {
+        e[u].push(v);
+        e[v].push(u);
+    }
+    e
+}
+
+fn dfs(e: &Vec<Vec<usize>>, dp: &mut Vec<usize>, u: usize, p: usize) {
+    dp[u] = 1;
+    for &v in e[u].iter() {
+        if v == p {
+            continue;
+        }
+        dfs(e, dp, v, u);
+        dp[u] += dp[v];
+    }
+}
+
+fn main() {
+    input! {
+        n: usize,
+        ab: [(Usize1, Usize1); n - 1],
+    };
+
+    let e = adjacency_list(n, &ab);
+    let mut dp = vec![0_usize; n];
+    dfs(&e, &mut dp, 0, 0);
+    let ans = dp.iter().map(|x| x * (n - x)).sum::<usize>();
+    println!("{}", ans);
+}