leetcode-5.14[414. 第三大的數、709. 轉換成小寫字母、766. 託普利茨矩陣]（python實現)

題目1

題解1

class Solution:
    def thirdMax(self, nums: List[int]) -> int:
        # 集合去重
        nums = list(set(nums))
        if len(nums) <= 2:
            return max(nums)
        # 三次選擇排序O(3n) -> O(n)
        for i in range(3):
            max_index = i
            for j in range(i+1, len(nums)):
                if nums[j] > nums[max_index]:
                    max_index = j
            nums[i], nums[max_index] = nums[max_index], nums[i]
        return nums[2]

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題目2

題解2

class Solution:
    def toLowerCase(self, str: str) -> str:
        for s in str:
            if ord(s) >= 65 and ord(s) <= 90:
                str = str.replace(s,chr(ord(s)+32))
        return str

        # 簡潔寫法
        # return ''.join([chr(ord(c)+32) if ord(c)>=65 and ord(c)<=90 else c for c in str])

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題目3

題解3

class Solution:
    def isToeplitzMatrix(self, matrix: List[List[int]]) -> bool: 
        # r1 - c1 == r2 - c2, 一組矩陣的x-y等於一個定值
        groups = {}
        for r, row in enumerate(matrix):
            for c, val in enumerate(row):
                if r-c not in groups:
                    groups[r-c] = val
                elif groups[r-c] != val:
                    return False
        return True

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