快排里的partition应用-找第k大的数字

int (vector<int>& nums, int low, int high)
{
    int x = nums[low];
    int i = low;
    int j = high-1;
    while(i<j)
    {
      while(i<j&&nums[j]<=x)
        j--;
      if(i<j)
        nums[i]=nums[j];
      while(i<j&&nums[i]>=x)
        i++;
      if(i<j)
        nums[j]=nums[i];
    }
    nums[i]=x;
    return i;
}

#include<vector>
using namespace std;

int (vector<int>& nums, int low, int high)
{
    int x = nums[low];
    int i = low;
    int j = high-1;
    while(i<j)
    {
      while(i<j&&nums[j]<=x)
        j--;
      if(i<j)
        nums[i]=nums[j];
      while(i<j&&nums[i]>=x)
        i++;
      if(i<j)
        nums[j]=nums[i];
    }
    nums[i]=x;
    return i;
}
    
int findKthLargest(vector<int>& nums, int k) {
    int begin = 0, end = nums.size();
    int target_num = 0;
    while (begin <= end){
        int pos = partition(nums, begin, end);
        if(pos == k-1){
            target_num = nums[pos];
            break;
        }
        else if(pos > k-1){
            end = pos;
        }
        else{
            begin = pos + 1;
        }
    }
    return target_num;
}


int main()
{
  vector<int> nums={2, 1};
  printf("%d", findKthLargest(nums, 2));
  getchar();
}