Add merge_sort to sort.rs

Author: whbrown

Diff for: labocédai/src/lib.rs

@@ -143,6 +143,10 @@ mod tests {
                 bubble_sort(&mut [29, 10, 14, 30, 37, 14, 18]),
                 [10, 14, 14, 18, 29, 30, 37]
             );
+            assert_eq!(
+                bubble_sort(&mut [-1, -2, 1, 0]),
+                [-2, -1, 0, 1]
+            );
             assert_eq!(bubble_sort(&mut []), []);
             assert_eq!(bubble_sort(&mut [1, 1, 1, 2, 1]), [1, 1, 1, 1, 2]);
             assert_eq!(bubble_sort(&mut [2, 1, 1, 1, 2]), [1, 1, 1, 2, 2]);
@@ -155,6 +159,10 @@ mod tests {
                 selection_sort(&mut [29, 10, 14, 30, 37, 14, 18]),
                 [10, 14, 14, 18, 29, 30, 37]
             );
+            assert_eq!(
+                selection_sort(&mut [-1, -2, 1, 0]),
+                [-2, -1, 0 ,1]
+            );
             assert_eq!(selection_sort(&mut []), []);
             assert_eq!(selection_sort(&mut [1, 1, 1, 2, 1]), [1, 1, 1, 1, 2]);
             assert_eq!(selection_sort(&mut [2, 1, 1, 1, 2]), [1, 1, 1, 2, 2]);
@@ -167,6 +175,10 @@ mod tests {
                 insertion_sort(&mut [29, 10, 14, 30, 37, 14, 18]),
                 [10, 14, 14, 18, 29, 30, 37]
             );
+            assert_eq!(
+                insertion_sort(&mut [-1, -2, 1, 0]),
+                [-2, -1, 0, 1]
+            );
             assert_eq!(insertion_sort(&mut []), []);
             assert_eq!(insertion_sort(&mut [1, 1, 1, 2, 1]), [1, 1, 1, 1, 2]);
             assert_eq!(insertion_sort(&mut [2, 1, 1, 1, 2]), [1, 1, 1, 2, 2]);
@@ -179,5 +191,22 @@ mod tests {
             assert_eq!(merge(&[], &[]), vec![]);
             assert_eq!(merge(&[1, 3, 5], &[2, 4, 6]), vec![1, 2, 3, 4, 5, 6]);
         }
+
+        #[test]
+        fn test_merge_sort() {
+            assert_eq!(
+                merge_sort(&mut [29, 10, 14, 30, 37, 14, 18]),
+                [10, 14, 14, 18, 29, 30, 37]
+            );
+            assert_eq!(
+                merge_sort(&mut [-1, -2, 1, 0]),
+                [-2, -1, 0, 1]
+            );
+            assert_eq!(merge_sort(&mut []), []);
+            assert_eq!(merge_sort(&mut [1, 1, 1, 2, 1]), [1, 1, 1, 1, 2]);
+            assert_eq!(merge_sort(&mut [2, 1, 1, 1, 2]), [1, 1, 1, 2, 2]);
+            assert_eq!(merge_sort(&mut [1]), [1]);
+        }
+
     }
 }

Diff for: labocédai/src/sort.rs

@@ -43,29 +43,38 @@ pub fn insertion_sort(nums: &mut [isize]) -> &mut [isize] {
     nums
 }
 
-pub fn merge(first_arr: &[isize], second_arr: &[isize]) -> Vec<isize> {
+pub fn merge(arr_1: &[isize], arr_2: &[isize]) -> Vec<isize> {
     /* merges two similarly sorted arrays */
-    let mut merged = Vec::with_capacity(first_arr.len() + second_arr.len());
+    let mut merged = Vec::with_capacity(arr_1.len() + arr_2.len());
     let mut i = 0;
     let mut j = 0;
-    while i < first_arr.len() && j < second_arr.len() {
-        if first_arr[i] <= second_arr[j] {
-            merged.push(first_arr[i]);
+    while i < arr_1.len() && j < arr_2.len() {
+        if arr_1[i] <= arr_2[j] {
+            merged.push(arr_1[i]);
             i += 1;
-        } else if first_arr[i] > second_arr[j] {
-            merged.push(second_arr[j]);
+        } else if arr_1[i] > arr_2[j] {
+            merged.push(arr_2[j]);
             j += 1;
         }
     }
     // push remaining values in unexhausted array into merged
-    if i < first_arr.len() {
-        for num in first_arr.iter().skip(i) {
-            merged.push(*num);
-        }
-    } else if j < second_arr.len() {
-        for num in second_arr.iter().skip(j) {
-            merged.push(*num);
-        }
+    while i < arr_1.len() {
+        merged.push(arr_1[i]);
+        i += 1;
+    }
+    while j < arr_2.len() {
+        merged.push(arr_2[j]);
+        j += 1;
     }
     merged
 }
+
+pub fn merge_sort(nums: &[isize]) -> Vec<isize> {
+    if nums.len() <= 1 {
+        return nums.to_vec();
+    }
+    let midpoint = nums.len() / 2;
+    let left = merge_sort(&nums[0..midpoint]);
+    let right = merge_sort(&nums[midpoint..]);
+    merge(&left, &right)
+}