InterviewBit - Strings: Reverse The String solution and README

Author: Lanh Hoang

Strings/Reverse_the_String/README.md

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+# Reverse the String
+
+## Problem:
+[https://www.interviewbit.com/problems/reverse-the-string](https://www.interviewbit.com/problems/reverse-the-string)
+
+Given an input string, reverse the string word by word.
+
+Example:
+
+**Input**
+```
+s = "the sky is blue"
+```
+
+**Output:**
+```
+"blue is sky the"
+```
+
+**NOTE:**
+
+A sequence of non-space characters constitutes a word.
+
+Your reversed string should not contain leading or trailing spaces, even if it is present in the input string.
+
+If there are multiple spaces between words, reduce them to a single space in the reversed string.
+
+## Approach:
+
+One simple approach is a two-pass solution:
+
+- First pass to split the string by spaces into an array of words
+- Second pass to extract the words in reversed order
+
+We can do better in one-pass. While iterating the string in reverse order, we keep track the beginning and the end position of a word.
+
+When we are at the beginning of a word, we append it.

Strings/Reverse_the_String/reverse_the_string.py

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+# https://www.interviewbit.com/problems/reverse-the-string
+
+# Python built-in function
+# class Solution:
+#   # @param A : string
+#   # @return string
+#   def reverseWords(self, A):
+#     A = A.split()
+#     A.reverse()
+#     return ' '.join(A)
+
+# Reverse in space
+class Solution:
+  # @param A : string
+  # @return string
+  def reverseWords(self, A):
+    left = -1
+    right = len(A) - 1
+    res = ''
+    while right >= 0:
+      while right >= 0 and A[right] == ' ':
+        right -= 1
+      
+      res += ' '
+      left = right
+
+      while left >= 0 and A[left] != ' ':
+        left -= 1
+      
+      res += A[left+1:right+1]
+      right = left
+    return res.strip()