added quick sort

Signed-off-by: yourarj <[email protected]>

 Date:      Thu Jan 4 08:26:20 2024 +0530

 On branch main

 Changes to be committed:
	modified:   Cargo.lock
	modified:   sorting-algorithms/Cargo.toml
	modified:   sorting-algorithms/src/lib.rs
	new file:   sorting-algorithms/src/quick_sort.rs

sorting-algorithms/Cargo.toml

@@ -1,5 +1,5 @@
 [package]
-name = "merge-sort"
+name = "sorting-algorithms"
 version = "0.1.0"
 edition = "2021"
 

sorting-algorithms/src/lib.rs

@@ -1,2 +1,3 @@
 pub mod insertion_sort;
 pub mod merge_sort;
+pub mod quick_sort;

sorting-algorithms/src/quick_sort.rs

@@ -0,0 +1,80 @@
+pub fn sort(arr: &mut [i32]) {
+    if arr.is_empty() {
+        return;
+    }
+    quick_sort(arr, 0, (arr.len() - 1) as isize);
+}
+
+fn quick_sort(arr: &mut [i32], start: isize, end: isize) {
+    if start > end {
+        return;
+    }
+
+    let pivot = arr[(start + (end - start) / 2) as usize];
+    let mut new_start = start;
+    let mut new_end = end;
+
+    while new_start <= new_end {
+        while arr[new_start as usize] < pivot {
+            new_start += 1;
+        }
+
+        while arr[new_end as usize] > pivot {
+            new_end -= 1;
+        }
+
+        if new_start <= new_end {
+            arr.swap(new_start as usize, new_end as usize);
+            new_start += 1;
+            new_end -= 1;
+        }
+    }
+
+    quick_sort(arr, start, new_end);
+    quick_sort(arr, new_start, end);
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn should_sort_reversed_array() {
+        let mut arr = [5, 4, 3, 2, 1, 0];
+        sort(&mut arr);
+
+        assert_eq!(arr[0], 0);
+        assert_eq!(arr[3], 3);
+        assert_eq!(arr[5], 5);
+    }
+
+    #[test]
+    fn should_sort_array_with_positive_negative_and_zero_numbers() {
+        let mut arr = [5, -4, 3, 2, -1, 0];
+        sort(&mut arr);
+
+        assert_eq!(arr[0], -4);
+        assert_eq!(arr[1], -1);
+        assert_eq!(arr[2], 0);
+        assert_eq!(arr[3], 2);
+        assert_eq!(arr[4], 3);
+        assert_eq!(arr[5], 5);
+    }
+
+    #[test]
+    fn should_not_touch_empty_array() {
+        let mut arr = [];
+        sort(&mut arr);
+        assert!(arr.is_empty());
+    }
+
+    #[test]
+    fn should_sort_array_with_multiple_duplicates_and_some_uniques() {
+        let mut arr = [5, 5, 5, 4, 4, 2, 2, 2, 2, 1, 0];
+        sort(&mut arr);
+
+        assert_eq!(arr[0], 0);
+        assert_eq!(arr[3], 2);
+        assert_eq!(arr[5], 2);
+    }
+}