随机快排实现：随机取pivot，保证时间复杂度

#include<iostream>
#include<vector>

using namespace std;

int partition(vector<int>& arr, int l, int r) {
	int pivot = arr[r];
	int i = l;
	for (int j = l; j < r; j++) {
		if (arr[j] <= pivot) {
			swap(arr[i++], arr[j]);
		}
	}
	swap(arr[i], arr[r]);
	return i;
}

int randomPartition(vector<int>& arr, int l, int r) {
	int pivotPos = (random() % (r - l + 1) + l);
	swap(arr[pivotPos], arr[r]);
	return partition(arr, l, r);
}

void quichRank(vector<int>& arr, int l, int r) {
	if (l <= r) {
		int pivotPos = randomPartition(arr, l, r);
		quichRank(arr, l, pivotPos - 1);
		quichRank(arr, pivotPos + 1, r);
	}
}

int main() {
	vector<int> arr;
	for (int i = 0; i < 1; i++) {
		arr.push_back(random()%100);
	}
	quichRank(arr, 0, arr.size() - 1);
	for (auto num : arr) {
		cout << num << " ";
	}
	return 0;
}