first commit

sort_closet/code-sorting/QuickSortOptimized.cpp

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+#include <iostream>
+#include <vector>
+#include <algorithm>
+
+using namespace std;
+
+// Helper to find median of three and swap pivot to the end
+int medianOfThree(vector<int> &nums, int low, int high, long long &comp_count, long long &move_count)
+{
+    int mid = low + (high - low) / 2;
+
+    comp_count++;
+    if (nums[low] > nums[mid])
+    {
+        swap(nums[low], nums[mid]);
+        move_count += 3;
+    }
+    comp_count++;
+    if (nums[low] > nums[high])
+    {
+        swap(nums[low], nums[high]);
+        move_count += 3;
+    }
+    comp_count++;
+    if (nums[mid] > nums[high])
+    {
+        swap(nums[mid], nums[high]);
+        move_count += 3;
+    }
+    
+    // Now nums[low] <= nums[mid] <= nums[high]
+    // Pivot is nums[mid], but we swap it with nums[high-1] to use in partition
+    // The partition logic will ignore the already sorted nums[low] and nums[high]
+    swap(nums[mid], nums[high]); // Move pivot to the end
+    move_count += 3;
+    return nums[high];
+}
+
+
+int partition_optimized(vector<int> &nums, int low, int high, long long &comp_count, long long &move_count)
+{
+    int pivot = medianOfThree(nums, low, high, comp_count, move_count);
+    int i = (low - 1);
+
+    for (int j = low; j <= high - 1; j++)
+    {
+        comp_count++;
+        if (nums[j] < pivot)
+        {
+            i++;
+            swap(nums[i], nums[j]);
+            move_count += 3;
+        }
+    }
+    swap(nums[i + 1], nums[high]);
+    move_count += 3;
+    return (i + 1);
+}
+
+void quickSortOptimizedHelper(vector<int> &nums, int low, int high, long long &comp_count, long long &move_count)
+{
+    if (low < high)
+    {
+        int pi = partition_optimized(nums, low, high, comp_count, move_count);
+        quickSortOptimizedHelper(nums, low, pi - 1, comp_count, move_count);
+        quickSortOptimizedHelper(nums, pi + 1, high, comp_count, move_count);
+    }
+}
+
+/*
+ * function   : implement quick sort with median-of-three pivot selection
+ * param nums : the vector to be sorted
+ * param comp_count : count of comparisons
+ * param move_count : count of moves
+ * return     : ---
+ */
+void QuickSortOptimized(vector<int> &nums, long long &comp_count, long long &move_count)
+{
+    if (nums.empty()) return;
+    quickSortOptimizedHelper(nums, 0, nums.size() - 1, comp_count, move_count);
+}