力扣日练-day2

1、盛最多水的容器  

  关键在于短板往里移可能变为长板容积增大，长板往里移一定变小，双指针，end和start，动态变化指针

class Solution:
    def maxArea(self, height: List[int]) -> int:
        max_v=0
        start=0
        end=len(height)-1
        while true:
            if start<end:
                v=min(height[start],height[end])*(end-start)
                max_v=max(v,max_v)
                if height[start]<height[end]:
                    start+=1
                else:
                    end-=1
            else:
                break
        return max_v

 

2、颜色分类

  关键在于颜色种类已知，可以利用Counter函数统计每个颜色的数量然后修改原始nums

class Solution:
    def sortColors(self, nums: List[int]) -> None:
        """
        Do not return anything, modify nums in-place instead.
        """
        s=Counter(nums)
        for i in range(s[0]):
            nums[i]=0
        for i in range(s[0],s[0]+s[1]):
            nums[i]=1
        for i in range(s[0]+s[1],s[0]+s[1]+s[2]):
            nums[i]=2

 

3、最长连续序列

class Solution:
    def longestConsecutive(self, nums: List[int]) -> int:
        nums=sorted(list(set(nums))
        max_len=0
        start=0
        if len(nums)==0:
           return 0
        for end in range(len(nums)):
           if end-start == nums[end] - nums[start]:
              max_len=max(max_len,end-start+1)
           else:         
              start=end
        return max_len

 

4、环形链表

 

#忽略了题目中的不能修改链表
class Solution:
    def detectCycle(self, head: ListNode) -> ListNode:
        h=head
        if h == None:
            return head
        while h != None:
            if h.val != '':
                h.val= ''
            else:
                return h 
            h = h.next
        return None

 

5、最小栈   列表模拟

class MinStack:
    def __init__(self):
        self.stack=[]
        self.min_stack=[]
    def push(self, val: int) -> None:
        self.stack.append(val)
        if len(self.stack)==1:
            self.min_stack.append(val)
        else:
            self.min_stack.append(min(val,self.min_stack[-1]))

    def pop(self) -> None:
        self.stack.pop()
        self.min_stack.pop()

    def top(self) -> int:
        return self.stack[-1]

    def getMin(self) -> int:
        return self.min_stack[-1]


# Your MinStack object will be instantiated and called as such:
# obj = MinStack()
# obj.push(val)
# obj.pop()
# param_3 = obj.top()
# param_4 = obj.getMin()