refactor: Apply fixable clippy suggestions

src/sorting/heap_sort.rs

@@ -21,14 +21,14 @@ fn heapify<T: Ord>(array: &mut [T]) {
 }
 
 fn siftdown<T: Ord>(array: &mut [T], mut root: usize, end: usize) {
-    while 2 * root + 1 <= end {
+    while 2 * root < end {
         let child = 2 * root + 1;
         let mut swap = root;
 
         if array[swap] < array[child] {
             swap = child;
         }
-        if child + 1 <= end && array[swap] < array[child + 1] {
+        if child < end && array[swap] < array[child + 1] {
             swap = child + 1;
         }
 

src/sorting/insertion_sort.rs

@@ -3,7 +3,7 @@ pub fn insertion_sort<T: Ord>(array: &mut [T]) {
         let mut j = i;
         while j > 0 && array[j] < array[j - 1] {
             array.swap(j, j - 1);
-            j = j - 1;
+            j -= 1;
         }
     }
 }

src/sorting/merge_sort.rs

@@ -1,6 +1,6 @@
 pub fn merge_sort<T: Ord + Copy>(array: &[T]) -> Vec<T> {
     if array.len() < 2 {
-        return array.iter().cloned().collect();
+        return array.to_vec();
     }
 
     let middle = array.len() / 2;
@@ -15,10 +15,10 @@ fn merge<T: Ord + Copy>(left: &mut Vec<T>, right: &mut Vec<T>) -> Vec<T> {
     let mut result = Vec::new();
 
     for _ in 0..left.len() + right.len() {
-        if left.len() == 0 {
+        if left.is_empty() {
             result.append(right);
             break;
-        } else if right.len() == 0 {
+        } else if right.is_empty() {
             result.append(left);
             break;
         } else if left[0] <= right[0] {

src/string_matching/knuth_morris_pratt.rs

@@ -10,7 +10,7 @@ fn precompute_table(pattern: &str) -> Vec<usize> {
         }
 
         if p[k] == p[q] {
-            k = k + 1;
+            k += 1;
         }
 
         pi[q] = k;
@@ -37,7 +37,7 @@ pub fn knuth_morris_pratt(text: &str, pattern: &str) -> Vec<usize> {
         }
 
         if p[q] == t[i - 1] {
-            q = q + 1;
+            q += 1;
         }
 
         if q == p.len() {