From fb08343f8c866dea2ec5e86a0dca8d091e33d146 Mon Sep 17 00:00:00 2001
From: ergz <emnlrodriguez@gmail.com>
Date: Thu, 17 Aug 2023 23:20:31 -0700
Subject: [PATCH] implement quicksort in c again to practice and in oding to
 see what its like

---
 c/qs.c         |  2 +-
 c/quicksort.c  | 51 ++++++++++++++++++++++++++++++++++++++++++++++++++
 odin/main.odin | 46 +++++++++++++++++++++++++++++++++++++++------
 3 files changed, 92 insertions(+), 7 deletions(-)
 create mode 100644 c/quicksort.c

diff --git a/c/qs.c b/c/qs.c
index 54a8efe..32fbfb4 100644
--- a/c/qs.c
+++ b/c/qs.c
@@ -38,7 +38,7 @@ void quick_sort(int arr[], int lo, int hi) {
 
 int main() {
     int array_len = 5;
-    int arr[5] = {5, 4, 3, 2, 1};
+    int arr[5] = {0, 2, 5, 1, 6};
     quick_sort(arr, 0, array_len - 1);
 
     printf("[ ");
diff --git a/c/quicksort.c b/c/quicksort.c
new file mode 100644
index 0000000..119a899
--- /dev/null
+++ b/c/quicksort.c
@@ -0,0 +1,51 @@
+#include <stdio.h>
+
+// the partition will weakly sort the array and return the index of
+// the pivot
+int partition(int arr[], int lo, int hi) {
+    int pivot_value = arr[hi];
+    int current_index = lo - 1;
+    int temp;
+    for (int i = lo; i < hi; i++) {
+        if (arr[i] <= pivot_value) {
+            current_index++;
+
+            temp = arr[i];
+            arr[i] = arr[current_index];
+            arr[current_index] = temp;
+        }
+    }
+
+    // once done with loop the current_index will hold
+    // the location where we need to place the pivot_value
+    current_index++;
+    arr[hi] = arr[current_index];
+    arr[current_index] = pivot_value;
+
+    return (current_index);
+}
+
+void qs(int arr[], int lo, int hi) {
+    if (lo < hi) {
+        int current_pivot = partition(arr, lo, hi);
+        qs(arr, lo, current_pivot - 1);
+        qs(arr, current_pivot + 1, hi);
+    }
+}
+
+void print_array(int arr[], int len) {
+    printf("[ ");
+    for (int i = 0; i < len; i++) {
+        printf("%d ", arr[i]);
+    }
+    printf("]\n");
+}
+
+int main() {
+    int arr[5] = {0, 2, 5, 1, 6};
+    print_array(arr, 5);
+    qs(arr, 0, 4);
+    print_array(arr, 5);
+
+    return (0);
+}
\ No newline at end of file
diff --git a/odin/main.odin b/odin/main.odin
index a71ac09..c1008a6 100644
--- a/odin/main.odin
+++ b/odin/main.odin
@@ -5,16 +5,50 @@ import "core:fmt"
 linear_search :: proc(arr: []int, len: int, needle: int) -> bool {
     for index, val in arr {
         if val == needle {
-            return true;
+            return true
         }
     }
-    return false;
+    return false
+}
+
+partition :: proc(arr: ^[]int, lo: int, hi: int) -> int {
+    pivot_value := arr[hi]
+    current_index := lo - 1
+
+    for i := lo; i < hi; i +=1 {
+        if arr[i] <= pivot_value {
+            current_index += 1
+            tmp := arr[i]
+            arr[i] = arr[current_index]
+            arr[current_index] = tmp
+        }
+    }
+
+    current_index += 1
+    arr[hi] = arr[current_index]
+    arr[current_index] = pivot_value
+
+    return(current_index)
+}
+
+quick_sort :: proc(arr: ^[]int, lo: int, hi: int) {
+    if lo < hi {
+        current_pivot := partition(arr, lo, hi);
+        quick_sort(arr, lo, current_pivot - 1);
+        quick_sort(arr, current_pivot + 1, hi);
+    }
 }
 
 main :: proc() {
-    fmt.println("hello there here is a for loop");
+    fmt.println("hello there here is a for loop")
 
-    values: []int = {1, 2, 3, 4, 5};
-    res: bool = linear_search(values, 5, 2);
-    fmt.println(res);
+    values: []int = {1, 2, 3, 4, 5}
+    res: bool = linear_search(values, 5, 2)
+    fmt.println(res)
+
+    fmt.println("quicksort ----------------")
+    arr: []int = {0, 2, 5, 1, 6}
+    fmt.println(arr);
+    quick_sort(&arr, 0, 4);
+    fmt.println(arr);
 }