目录

学习目标

学习内容

738.单调递增的数字 

 968.监控二叉树 

 总结

---

学习目标

学习内容

738.单调递增的数字 

738. 单调递增的数字 - 力扣（LeetCode）https://leetcode.cn/problems/monotone-increasing-digits/

class Solution:
    def monotoneIncreasingDigits(self, n: int) -> int:
        s = list(str(n))
        for i in range(len(s)-1,0,-1):
            if int(s[i])<int(s[i-1]):
                s[i-1] = str(int(s[i-1])-1)
                s[i:] = ["9"]*(len(s)-i)
        return int("".join(s))

 968.监控二叉树 

968. 监控二叉树 - 力扣（LeetCode）https://leetcode.cn/problems/binary-tree-cameras/

# Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, val=0, left=None, right=None):
#         self.val = val
#         self.left = left
#         self.right = right
class Solution:
    def minCameraCover(self, root: Optional[TreeNode]) -> int:
        res = 0
        def dfs(root):
            nonlocal res
            if not root:return 2
            left = dfs(root.left)
            right = dfs(root.right)
            if left==2 and right==2:
                return 0
            elif left==0 or right==0:
                res+=1
                return 1
            elif left==1 or right==1:
                return 2
        if dfs(root)==0:
            res+=1
        return res

 总结

problems/贪心算法总结篇.md · programmercarl/leetcode-master（代码随想录出品） - Gitee.comhttps://gitee.com/programmercarl/leetcode-master/blob/master/problems/%E8%B4%AA%E5%BF%83%E7%AE%97%E6%B3%95%E6%80%BB%E7%BB%93%E7%AF%87.md#%E8%B4%AA%E5%BF%83%E7%AE%97%E6%B3%95%E6%80%BB%E7%BB%93%E7%AF%87