add: files so far

d1/d1p2.rs

@@ -0,0 +1,21 @@
+use std::collections::HashMap;
+use std::io;
+
+fn main() -> io::Result<()> {
+    let mut l1: Vec<u64> = vec!();
+    let mut l2: HashMap<u64, u64> = HashMap::default();
+    for line in io::stdin().lines() {
+        let line = line?;
+        let parts: Vec<&str> = line.trim().split_whitespace().collect();
+        let (n1, n2) = (parts[0], parts[1]);
+        l1.push(n1.parse().unwrap());
+        let v = l2.entry(n2.parse::<u64>().unwrap()).or_insert(0);
+        *v += 1;
+    }
+    let mut sum = 0;
+    for n1 in l1.into_iter() {
+        sum += n1*l2.get(&n1).unwrap_or(&0);
+    }
+    println!("{}", sum);
+    Ok(())
+}