diff --git a/2022/src/day4.rs b/2022/src/day4.rs
index 336ad76..5b6c47b 100644
--- a/2022/src/day4.rs
+++ b/2022/src/day4.rs
@@ -4,34 +4,25 @@ use std::collections::HashSet;
 const INPUT: &str = include_str!("../data/day4.txt");
 
 pub fn part1() -> String {
-    format!("{}", count_full_containments(input(INPUT)))
+    format!("{}", count_full_containments(&input(INPUT)))
 }
 
 pub fn part2() -> String {
-    format!("{}", count_overlaps(input(INPUT)))
+    format!("{}", count_overlaps(&input(INPUT)))
 }
 
-fn count_full_containments(pairings: Vec<ElfPairing>) -> u32 {
-    pairings.into_iter().fold(0, |cur, pairing| {
-        if pairing.has_full_containment() {
-            cur + 1
-        } else {
-            cur
-        }
-    })
+fn count_full_containments(pairings: &Vec<ElfPairing>) -> u32 {
+    pairings
+        .into_iter()
+        .filter(|pairing| pairing.has_full_containment())
+        .count() as u32
 }
 
-fn count_overlaps(pairings: Vec<ElfPairing>) -> u32 {
-    pairings.into_iter().fold(
-        0,
-        |cur, pairing| {
-            if pairing.has_overlap() {
-                cur + 1
-            } else {
-                cur
-            }
-        },
-    )
+fn count_overlaps(pairings: &Vec<ElfPairing>) -> u32 {
+    pairings
+        .into_iter()
+        .filter(|pairing| pairing.has_overlap())
+        .count() as u32
 }
 
 struct ElfPairing {
@@ -132,7 +123,7 @@ mod test {
     #[test]
     fn it_counts_full_containments() {
         with_input(|pairings| {
-            assert_eq!(2, count_full_containments(pairings));
+            assert_eq!(2, count_full_containments(&pairings));
         });
     }
 
@@ -147,4 +138,11 @@ mod test {
             assert!(pairings[5].has_overlap());
         });
     }
+
+    #[test]
+    fn it_checks_part1() {
+        let pairings = input(INPUT);
+        assert_eq!(466, count_full_containments(&pairings));
+        assert_eq!(865, count_overlaps(&pairings));
+    }
 }