leetcode75

class Solution {
public:
    void sortColors(vector<int>& nums) {
        sort(nums.begin(), nums.end());
    }
};

上面这个太弱了，给一个强不了多少的

 class Solution:
     def sortColors(self, nums: 'List[int]') -> 'None':
         red = 0
         white = 0
         blue = 0
         for n in nums:
             if n == 0:
                 red+=1
             elif n == 1:
                 white += 1
             elif n == 2:
                 blue += 1
             else:
                 print('error')
         nums.clear()
         nums.extend([0]*red + [1]*white + [2]*blue)

下面给出一个比较强的

 class Solution:
     def swap(self,nums,i,j):
         nums[i],nums[j] = nums[j],nums[i]
         '''
         temp = nums[i]
         nums[i] = nums[j]
         nums[j] = temp
         '''

     def sortColors(self, nums: 'List[int]') -> 'None':
         n = len(nums)
         left = 0
         right = n - 1
         i = 0
         while i <= right:
             if nums[i] == 0:
                 if i != left:
                     self.swap(nums,i,left)
                 i += 1
                 left += 1
             elif nums[i] == 1:
                 i += 1
             else:
                 self.swap(nums,i,right)

注意swap的写法，如果用temp来存，速度会慢很多。