alternative

src/bin/1.rs

@@ -36,51 +36,65 @@ Of course, your expense report is much larger. Find the two entries that sum to
 do you get if you multiply them together?
 */
 
-use std::fs::{File};
-use std::collections::HashSet;
-use std::io::{BufRead, BufReader};
 use anyhow::Result;
+use std::collections::HashSet;
+use std::fs::File;
+use std::io::{BufRead, BufReader};
 
-fn find_triple(target: i32, list: &Vec<i32>, set: &HashSet<i32>) -> i32 {
-    for i in list {
-        let product = find_pair(target - i, list, set);
-        if product > 0 {
-            return product * i;
-        }
-    }
-    0
+struct Entries {
+    list: Vec<i32>,
+    set: HashSet<i32>,
 }
 
-fn find_pair(target: i32, list: &Vec<i32>, set: &HashSet<i32>) -> i32 {
-    for i in list {
-        if i > &target {
-            break
-        }
-        let val = target - i;
-        if set.contains(&val) {
-            return i * val;
+impl Entries {
+    fn find_triple(&self, target: i32) -> i32 {
+        for i in self.list.iter().copied() {
+            let product = self.find_pair(target - i);
+            if product > 0 {
+                return product * i;
+            }
         }
+        0
+    }
+
+    fn find_pair(&self, target: i32) -> i32 {
+        for i in self.list.iter().copied() {
+            if i > target {
+                break;
+            }
+            let val = target - i;
+            if self.set.contains(&val) {
+                return i * val;
+            }
+        }
+        0
+    }
+}
+
+impl std::iter::FromIterator<i32> for Entries {
+    fn from_iter<T>(iter: T) -> Self
+    where
+        T: IntoIterator<Item = i32>,
+    {
+        let mut list = Vec::new();
+        let mut set = HashSet::new();
+        for value in iter {
+            list.push(value);
+            set.insert(value);
+        }
+        list.sort();
+        Entries { list, set }
     }
-    0
 }
 
 fn main() -> Result<()> {
     //let contents = fs::read_to_string("1.input").expect("Couldn't read \"1.input\"");
-    let file = File::open("1.input")?;
-    let reader = BufReader::new(file);
+    let entries: Entries = BufReader::new(File::open("1.input")?)
+        .lines()
+        .filter_map(|line| line.ok()?.parse().ok())
+        .collect();
 
-    let mut list: Vec<i32> = Vec::new();
-    let mut set: HashSet<i32> = HashSet::new();
-
-    for line in reader.lines() {
-        let value = line?.parse::<i32>()?;
-        list.push(value);
-        set.insert(value);
-    }
-
-    list.sort();
-
-    println!("Pair is {}", find_pair(2020, &list, &set));
-    println!("Triple is {}", find_triple(2020, &list, &set));
+    println!("Pair is {}", entries.find_pair(2020));
+    println!("Triple is {}", entries.find_triple(2020));
     Ok(())
 }