提供了兩種基準值的取值方法:
1. 隨機選取元素作爲基準值
2. 區間的左中右三端三個數,取其中值作爲基準值
代碼如下:
#include <iostream>
#include <random>
#include <vector>
#include <ctime>
#include <cstdlib>
#define NUM 10
using namespace std;
void quickSort(vector<int>& nums, int lo, int hi) {
if(lo >= hi) return;
int left = lo, right = hi;
// //隨機選取元素作爲基準值
// srand(time(NULL));
// int idx = rand() % (hi - lo) + lo;
// swap(nums[left], nums[idx]);
// int tmp = nums[left];
//left, right, mid 三數取中間值作爲基準值
int mid = (left + right) >> 1;
if(nums[left]<nums[mid]) swap(nums[left], nums[mid]);
if(nums[right]<nums[mid]) swap(nums[right], nums[mid]);
if(nums[left]>nums[right]) swap(nums[left], nums[right]);
int tmp = nums[left];
while(lo < hi) {
while(hi > lo && nums[hi] >= tmp) hi--;
nums[lo] = nums[hi];
while(hi > lo && nums[lo] < tmp) lo++;
nums[hi] = nums[lo];
}
nums[lo] = tmp;
quickSort(nums, left, lo - 1);
quickSort(nums, lo + 1, right);
}
int main() {
auto t1=clock();
vector<int> nums(NUM); // 10 65 8 3 5 7 5 11 6 33
for(auto& num : nums) cin >> num;
//遞歸實現
quickSort(nums, 0, nums.size() - 1);
cout << "time cost : " << clock()-t1 << " ms" << endl;
//非遞歸實現待補充
for(auto num : nums) cout << num << " ";
return 0;
}