Collection of common algorithm questions in test post interview

    def pra_01(self):
        #  Give you an array of integers nums , Where the elements have been arranged in ascending order , Please convert it into a highly balanced tree 
        #  Binary search tree . Highly balanced 
        #  A binary tree is a tree that satisfies 「 The absolute value of the height difference between the left and right subtrees of each node does not exceed 1 」 Two fork tree .
        nums = [1,2,3,4,5]

    def pra_02(self):
        #  Given a string , Verify that it is a palindrome string , Consider only alphabetic and numeric characters , The case of letters can be ignored 
        str = 'Aabffbaa'
        if str.lower() == str[::-1].lower():print('yes')

    def pra_03(self):
        #  Given an array of non-empty integers , Except that an element only appears once , Each of the other elements occurs twice . Find the element that only appears once .
        #  explain ： Your algorithm should have linear time complexity . Can you do this without using extra space ？
        nums = [1,2,2,3,3]
        result = 0
        for num in nums:result = result ^ num
        print(result)

    def pra_04(self):
        #  Given a string , Find the character that appears most often 
        s = 'abca'
        l = list(s)
        max = 0
        result = ''
        for i in range(0,len(l)-1):
            sum = 0
            print(l[i],l[i+1])
            for j in range(i+1,len(l)-2):
                if l[i] == l[j]:sum=sum+1
            if sum>max: max = sum;result = l[i]
        print(max,result)