LeetCode 209 周赛

5531. 特殊数组的特征值

class Solution:
    def specialArray(self, nums: List[int]) -> int:
        n = len(nums)
        for i in range(n + 1):
            c = 0
            for num in nums:
                if num >= i:
                    c += 1
            if c == i:
                return i
        return -1

5532. 奇偶树

class Solution:
    def isEvenOddTree(self, root: TreeNode) -> bool:
        q, nq = [root], []
        flag = True
        while q:
            if flag:
                pre = float('-inf')
                for node in q:
                    if node.val & 1 == 0 or node.val <= pre:
                        return False
                    pre = node.val
                    if node.left:
                        nq.append(node.left)
                    if node.right:
                        nq.append(node.right)
            else:
                pre = float('inf')
                for node in q:
                    if node.val & 1 == 1 or node.val >= pre:
                        return False
                    pre = node.val
                    if node.left:
                        nq.append(node.left)
                    if node.right:
                        nq.append(node.right)
            q, nq = nq, []
            flag = not flag
        return True

5534. 可见点的最大数目

class Solution:
    def visiblePoints(self, points: List[List[int]],
                      angle: int, location: List[int]) -> int:
        import math
        angle = angle / 360 * 2 * math.pi
        cnt = 0
        a = []
        for x, y in points:
            if x == location[0] and y == location[1]:
                cnt += 1
            else:
                xx, yy = x - location[0], y - location[1]
                a.append(math.atan2(yy, xx))
        a.sort()
        n = len(a)
        b = [x + math.pi * 2 for x in a]
        a += b
        j = 0

        ret = 0
        for i in range(n):
            while j < len(a):
                if a[j] - a[i] > angle:
                    break
                j += 1
            ret = max(ret, j - i)
        return ret + cnt

5533. 使整数变为 0 的最少操作次数

class Solution:
    def minimumOneBitOperations(self, n: int) -> int:
        ans = 0
        while n:
            ans ^= n
            n >>= 1
        return ans

class Solution:
    def minimumOneBitOperations(self, n: int) -> int:
        if n == 0:
            return 0
        p = n.bit_length()
        return (1 << p) - 1 - self.minimumOneBitOperations(n - (1 << (p - 1)))

两种做法