feat: implement merge sort

src/lib.rs

@@ -34,6 +34,53 @@ pub fn selection_sort(mut numbers: Vec<i32>) -> Vec<i32> {
     numbers
 }
 
+pub fn merge_sort(numbers: &mut Vec<i32>, left: i32, right: i32) {
+    if left >= right {
+        return;
+    }
+
+    let mid = (left + right) / 2;
+    merge_sort(numbers, left, mid);
+    merge_sort(numbers, mid + 1, right);
+    merge(numbers, left, mid, right);
+}
+
+fn merge(numbers_to: &mut Vec<i32>, left: i32, middle: i32, right: i32) {
+    let left_mid: std::ops::Range<usize> = (left as usize)..(middle as usize);
+    let mid_right: std::ops::Range<usize> = (middle as usize)..(right as usize);
+
+    let vec_l = numbers_to[left_mid].to_vec(); // Clone the left part
+    let vec_r = numbers_to[mid_right].to_vec(); // Clone the right part
+
+    let (mut i, mut j) = (0, 0);
+    let mut k = left;
+
+    while i < vec_l.len() && j < vec_r.len() {
+        if vec_l[i as usize] <= vec_r[j as usize] {
+            numbers_to[k as usize] = vec_l[i as usize];
+            i += 1;
+        } else {
+            numbers_to[k as usize] = vec_r[j as usize];
+            j += 1;
+        }
+        k += 1;
+    }
+
+    // Copy remaining elements from vec_l
+    while i < vec_l.len() {
+        numbers_to[k as usize] = vec_l[i as usize];
+        i += 1;
+        k += 1;
+    }
+
+    // Copy remaining elements from vec_r
+    while j < vec_r.len() {
+        numbers_to[k as usize] = vec_r[j as usize];
+        j += 1;
+        k += 1;
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
@@ -42,7 +89,6 @@ mod tests {
     fn it_insertion_sort() {
         let numbers = vec![5, 2, 4, 6, 1, 3];
         let sorted_numbers = insertion_sort(numbers);
-        dbg!(&sorted_numbers);
 
         assert_eq!(sorted_numbers, vec![1, 2, 3, 4, 5, 6]);
     }
@@ -51,8 +97,16 @@ mod tests {
     fn it_selection_sort() {
         let numbers = vec![5, 2, 4, 6, 1, 3];
         let sorted_numbers = selection_sort(numbers);
-        dbg!(&sorted_numbers);
 
         assert_eq!(sorted_numbers, vec![1, 2, 3, 4, 5, 6]);
     }
+
+    #[test]
+    fn it_merge_sort() {
+        let mut numbers: Vec<i32> = vec![11, 12, 13, 5, 6, 7];
+        let (left, right) = (0, numbers.len() as i32);
+        merge_sort(&mut numbers, left, right);
+
+        assert_eq!(numbers, vec![5, 6, 7, 11, 12, 13]);
+    }
 }