规律问题

下面记录一下我遇到的一些找规律的问题

0X00 总结

• 319. Bulb Switcher

from math import sqrt
class Solution:
    def bulbSwitch(self, n: int) -> int:
        return int(sqrt(n))

• 6. ZigZag Conversion

class Solution:
    def convert(self, s: str, numRows: int) -> str:
        if not s or numRows <= 1: return s
        temp = [[] for _ in range(numRows) ]
        dirs = 1
        index = 0
        for c in s:
            temp[index].append(c)
            index += dirs
            if index == 0 or index == numRows-1:
                dirs *= -1
        
        ans = []
        for line in temp:
            ans += line
        
        return "".join(ans)

• 48. Rotate Image

class Solution:
    def rotate(self, matrix: List[List[int]]) -> None:
        """
        Do not return anything, modify matrix in-place instead.
        """
        # 先翻转
        # 在沿正对角线交换元素
        if len(matrix) == 0: return 
        m, n = len(matrix), len(matrix[0])
        matrix[:] = matrix[::-1]
        for x in range(m):
            for y in range(x+1, n):
                matrix[x][y], matrix[y][x] = matrix[y][x], matrix[x][y]