快速排序

快速排序：
在数组nums随机总选中一个数做对比nums[index]；将数组nums中小于nums[index]的元素放在数组的左侧，将数组中大于nums[index]的元素放在数组的右侧；再分别对小于nums[index]序列和大于nums[index]的序列进行排序。代码如下：

#include <stdio.h>
#include <vector>
#include <algorithm>
#include <stdlib.h>
#include <time.h>

using namespace std;
class Solution {
public:
    int get_rand_num(int start, int end) {
        return (rand() % (end-start+1))+ start;
    }

    void swap(vector<int>& nums, int a, int b) {
        int tmp = nums[a];
        nums[a] = nums[b];
        nums[b] = tmp;
    }

    int partition(vector<int>& nums, int start, int end) {
        if (start >= end) {
            return -1;
        }

        int tmp_index = get_rand_num(start, end);
        swap(nums, tmp_index, end);

        int small = start -1;
        for (int index = start; index < end; index++) {
            if (nums[index] < nums[end]) {
                if (index != small) {
                    small++;
                    swap(nums, small, index);
                }

            }
        }
        ++small;
        swap(nums, small, end);
        return small;
    }
       int quick_sort(vector<int>& nums, int start, int end) {
        if (start < 0 || end >= nums.size() || start >= end ) {
            return start;
        }
        int index = partition(nums, start, end);
        if (index > start && index < nums.size()) {
            quick_sort(nums, start, index -1);
        }
        if (index < end && index > 0) {
            quick_sort(nums, index + 1, end);
        }
        return index;
    }

    vector<int> sortArray(vector<int>& nums) {
        int size = nums.size();
        if (size ==0 ) {
            return nums;
        }

        quick_sort(nums, 0, size -1);

        return nums;
    }
};


int main()
{
    Solution solution;
    std::vector<int> nums = {5,1,1,2,0,0};
    solution.sortArray(nums);

    for (int i = 0; i < nums.size(); i++)
    {
        printf("%d",nums[i]);
    }
}