LC709. To Lower Case

class Solution:
    def toLowerCase(self, str: str) -> str:
        # main idea: buitin lower()
        """ O(N)/O(N)
        """
        li = [] 
        for c in str:
            if 'A'<=c<='Z':
                c = chr(ord(c)+32)
            li.append(c)
        return ''.join(li)

class Solution:
    def toLowerCase(self, str: str) -> str:
        # main idea: ASCII 
        """ O(N)/O(N)
        """
        li = [] 
        for c in str:
            if 'A'<=c<='Z':
                c = chr(ord(c)+32)
            li.append(c)
        return ''.join(li)