AC atcoder/abc325/d

Cargo.toml

@@ -818,3 +818,7 @@ path = "atcoder/abc323/e/main.rs"
 [[bin]]
 name = "atcoder-abc324-d-main"
 path = "atcoder/abc324/d/main.rs"
+
+[[bin]]
+name = "atcoder-abc325-d-main"
+path = "atcoder/abc325/d/main.rs"

atcoder/abc325/d/main.rs

@@ -0,0 +1,149 @@
+// AC
+
+// https://atcoder.jp/contests/abc325/tasks/abc325_d
+
+use std::collections::BTreeMap;
+
+fn main() {
+    // n ~ 10^5
+    // t, d ~ 10^18
+    let n: usize = read_vec()[0];
+
+    let mut groups: BTreeMap<usize, Vec<usize>> = BTreeMap::new();
+    for _ in 0..n {
+        let [t, d]: [usize; 2] = read_array();
+        groups.entry(t).or_default().push(t + d);
+    }
+
+    // greedily pick first one to expire
+    let mut t = 0;
+    let mut result = 0;
+    let mut remainings = Multiset::new();
+
+    loop {
+        if let Some(group) = groups.get(&t) {
+            for &v in group {
+                remainings.insert(v);
+            }
+            groups.remove(&t);
+        }
+
+        // clear expired ones
+        while let Some(&f) = remainings.first() {
+            if f >= t {
+                break;
+            }
+            remainings.pop_first();
+        }
+
+        // pick first one
+        if let Some(_) = remainings.first() {
+            t += 1;
+            result += 1;
+            remainings.pop_first();
+            continue;
+        }
+
+        // if nothing, fast-forward to next group
+        if let Some((&next, _)) = groups.first_key_value() {
+            t = next;
+            continue;
+        }
+        break;
+    }
+
+    println!("{}", result);
+}
+
+// TODO: generalize?
+#[derive(Debug)]
+struct Multiset {
+    map: BTreeMap<usize, usize>,
+}
+
+impl Multiset {
+    fn new() -> Self {
+        Self {
+            map: BTreeMap::new(),
+        }
+    }
+
+    fn insert(&mut self, v: usize) {
+        *self.map.entry(v).or_default() += 1;
+    }
+
+    fn first(&mut self) -> Option<&usize> {
+        self.map.first_key_value().map(|kv| kv.0)
+    }
+
+    fn pop_first(&mut self) {
+        if let Some(mut entry) = self.map.first_entry() {
+            let v = entry.get_mut();
+            assert!(*v > 0);
+            if *v > 1 {
+                *v -= 1;
+            } else {
+                entry.remove();
+            }
+        }
+    }
+}
+
+/*
+python misc/run.py atcoder/abc325/d/main.rs
+
+%%%% begin
+5
+1 1
+1 1
+2 1
+1 2
+1 4
+%%%%
+4
+%%%% end
+
+%%%% begin
+2
+1 1
+1000000000000000000 1000000000000000000
+%%%%
+2
+%%%% end
+
+%%%% begin
+10
+4 1
+1 2
+1 4
+3 2
+5 1
+5 1
+4 1
+2 1
+4 1
+2 4
+%%%%
+6
+%%%% end
+*/
+
+//
+// utils
+//
+
+#[allow(dead_code)]
+fn read_vec<T: std::str::FromStr>() -> Vec<T> {
+    let mut line = String::new();
+    std::io::stdin().read_line(&mut line).unwrap();
+    line.split_whitespace()
+        .map(|s| s.parse().ok().unwrap())
+        .collect()
+}
+
+#[allow(dead_code)]
+fn read_array<T: std::str::FromStr, const LEN: usize>() -> [T; LEN] {
+    #[allow(unused_imports)]
+    use std::convert::TryInto;
+    read_vec::<T>().try_into().ok().unwrap()
+}