LC 0151 [M] Reverse Words in a String - ALawliet/algorithms GitHub Wiki

class Solution:
    def reverseWords(self, s: str) -> str:
        return ' '.join(s.split()[::-1])

class Solution(object):
    def reverseWords(self, s):
        arr = list(s)
        self.reverse_string(arr, 0, len(arr)-1)
        self.reverse_word(arr)
        word = self.trim_sides(arr)
        res = self.trim_space(word)
        return ''.join(res)


    def reverse_string(self, arr, l, r):
        '''reverse a given string'''
        while l < r:
            arr[l], arr[r] = arr[r], arr[l]
            l += 1 ; r -= 1
        return arr
    
    
    def reverse_word(self, arr):
        '''reverse every words in a string'''
        l, r = 0 , 0
        while r < len(arr):
            while r < len(arr) and not arr[r].isspace(): r += 1
            self.reverse_string(arr, l, r-1)
            r += 1; l = r
        return arr
    
    def trim_sides(self, arr):
        '''str.strip() basically'''
        if ''.join(arr).isspace(): return []
        l , r = 0, len(arr) - 1
        while l < r and arr[l].isspace(): l += 1
        while l < r and arr[r].isspace(): r -= 1
        return arr[l:r+1]
    
    def trim_space(self, word):
        '''remove duplicating space in a word'''
        if not word: return []
        res = [word[0]]            
        for i in range(1, len(word)):
            if res[-1].isspace() and word[i].isspace(): continue
            res.append(word[i])
        return res

class Solution:
    def reverseWords(self, s: str) -> str:
        def rev(s, l, r):
            while l < r:
                s[l], s[r] = s[r], s[l]
                l += 1
                r -= 1
            return
        
        def rev_words(s):
            i = 0
            while i < len(s):
                while i < len(s) and s[i] == ' ':
                    i += 1
                if i == len(s):
                    break
                # s[i] starts a word, now find j that ends a word
                j = i
                while j+1 < len(s) and s[j+1] != ' ':
                    j += 1
                # s[j] ends a word
                rev(s, i, j)
                i = j + 1
        
        def trim(s):
            i, j = 0, 0 # j to be checked, i holds index of next chr
            for j in range(len(s)):
                if s[j] != ' ':
                    if i > 0 and j > 0 and s[j-1] == ' ': # this is key, to determine if we need add a space or not.
                        s[i] = ' '
                        i += 1
                    s[i] = s[j]
                    i += 1
            return s[:i]
                    
        sentence = list(s)
        rev(sentence, 0, len(sentence)-1)
        rev_words(sentence)
        arr = trim(sentence)
        return ''.join(arr)