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