diff --git a/source/first_missing_positive/mod.rs b/source/first_missing_positive/mod.rs
index c9df8d7..c4d5eac 100644
--- a/source/first_missing_positive/mod.rs
+++ b/source/first_missing_positive/mod.rs
@@ -1,16 +1,21 @@
-pub fn first_missing_positive(mut numbers: Vec<i32>) -> i32 {
+pub fn first_missing_positive(numbers: Vec<i32>) -> i32 {
   let numbers_length = numbers.len();
 
   // Mark all numbers below 1 and above the maximum range as i32::MAX.
-  for index in 0..numbers_length {
-    if numbers[index] < 1 || numbers[index] > numbers_length as i32 {
-      numbers[index] = i32::MAX;
-    }
-  }
+  let mut numbers = numbers
+    .into_iter()
+    .map(|number| {
+      if number < 1 || number > numbers_length as i32 {
+        i32::MAX
+      } else {
+        number
+      }
+    })
+    .collect::<Vec<_>>();
 
   for index in 0..numbers_length {
     // For each index get its number and subtract 1.
-    let index = numbers[index].abs() as usize - 1;
+    let index = numbers[index].unsigned_abs() as usize - 1;
 
     // If that index then isn't i32::MAX - 1 (ie. negative or above range).
     if index as i32 != i32::MAX - 1 {
@@ -32,5 +37,5 @@ pub fn first_missing_positive(mut numbers: Vec<i32>) -> i32 {
         None
       }
     })
-    .unwrap_or_else(|| numbers_length + 1) as i32
+    .unwrap_or(numbers_length + 1) as i32
 }
diff --git a/source/valid_number/mod.rs b/source/valid_number/mod.rs
index 8351df6..01a82bf 100644
--- a/source/valid_number/mod.rs
+++ b/source/valid_number/mod.rs
@@ -5,7 +5,7 @@ pub fn is_number(string: String) -> bool {
     return false;
   }
 
-  let mut parts = string.split("e");
+  let mut parts = string.split('e');
 
   let valid_significand = match parts.next() {
     Some(part) => part.parse::<f64>().is_ok(),
diff --git a/source/word_pattern/mod.rs b/source/word_pattern/mod.rs
index 1ce3d5b..937c4ac 100644
--- a/source/word_pattern/mod.rs
+++ b/source/word_pattern/mod.rs
@@ -5,7 +5,7 @@ pub fn word_pattern(pattern: String, string: String) -> bool {
   let mut pattern_iter = pattern.chars();
   let mut string_iter = string.split_whitespace();
 
-  if pattern.len() != string_iter.clone().collect::<Vec<_>>().len() {
+  if pattern.len() != string_iter.clone().count() {
     return false;
   }