[剑指Offer] 29.最小的K个数

【思路1】全排序（快排）之后取出前K个数。O(K+nlogn)

 class Solution
 {
 public:
     vector<int> GetLeastNumbers_Solution(vector<int> input, int k)
     {
         vector<int> res;
         if(k > input.size())
             return res;
         sort(input.begin(),input.end());
         for(int i = ; i < k; i ++)
             res.push_back(input[i]);
         return res;
     }
 };

【思路2】冒泡排序的思想，但不用全排序，只要找出K个即可

 class Solution
 {
 public:
     void swap(int& x,int& y)
     {
         int temp = x;
         x = y;
         y = temp;
     }
     vector<int> GetLeastNumbers_Solution(vector<int> input, int k)
     {
         vector<int> res;
         int size = input.size();
         if(k > size)
             return res;
         for(int i = ; i < k; i ++)
         {
             for(int j = ; j < size - i - ; j ++)
             {
                 if(input[j + ] > input[j])
                 {
                     swap(input[j + ],input[j]);
                 }
             }
             res.push_back(input[size - i - ]);
         }
         return res;
     }
 };