day9:python uniquechars

Author: mandliya

README.md

@@ -7,10 +7,10 @@
 | Current Status|     Stats     |
 | :------------: | :----------: |
 | Total C++ Problems | 188 |
-| Total Python Problems | 13 |
-| Current Daily Streak| 8 |
+| Total Python Problems | 14 |
+| Current Daily Streak| 9 |
 | Last Streak | 06/20/2019 - 06/21/2019|
-| Current Streak | 06/23/2019 - 06/30/2019|
+| Current Streak | 06/23/2019 - 07/01/2019|
 
 </center>
 
@@ -82,7 +82,7 @@ Include contains single header implementation of data structures and some algori
 ### Cracking the coding interview problems
 | Problem | Solution |
 | :------------ | :----------: |
-| Problem 1-1 : Edition 6: Write an algorithm to determine whether a string has unique characters or not. Can we do it without using additional data structures? | [1-1-hasUniqueChars.cpp](cracking_the_coding_interview_problems/1-1-hasUniqueChars.cpp)|
+| Problem 1-1 : Edition 6: Write an algorithm to determine whether a string has unique characters or not. Can we do it without using additional data structures? | [1-1-hasUniqueChars.cpp](cracking_the_coding_interview_problems/1-1-hasUniqueChars.cpp), [1-1-hasUniqueChars.py](cracking_the_coding_interview_problems/1-1-hasUniqueChars.py)|
 | Problem 1-2 : Edition 5: Reverse a string when you are a pass a null terminated C string.|[1-2-edi5-reverseString.cpp ](cracking_the_coding_interview_problems/1-2-edi5-reverseString.cpp)|
 | Problem 1-2 : Edition 6: Given two strings, determine if one is permutation of other.|[1-2-perm-strings.cpp](cracking_the_coding_interview_problems/1-2-perm-strings.cpp)|
 | Problem 1-3 : Edition 5: Write an algorithm to remove duplicate chars from a string.|[1-3-edi5-removeDuplicates.cpp](cracking_the_coding_interview_problems/1-3-edi5-removeDuplicates.cpp)|

cracking_the_coding_interview_problems/1-1-hasUniqueChars.py

@@ -0,0 +1,52 @@
+"""
+ Cracking the coding interview, edition 6
+ Problem 1.1
+ Write an algorithm to determine whether a string has unique characters or not
+ Can we do it without using additional data structures?
+"""
+
+def is_unique(string):
+    """ Checks if string has unique characters.
+    Args:
+        string: the string which needs to be checked for unique characters.
+        This string only contains a-z lowercase (26 chars).
+        'check' is 32-bit integer, 1 bit per alphabet.
+    Returns:
+        True if string has unique characters False otherwise
+
+    """
+    check = 0
+    for char in string:
+        c = ord(char) - ord('a')
+        if check & (1 << c) :
+            return False
+        check |= (1 << c)
+    return True
+
+def is_unique2(string):
+    """ Checks if string has unique characters
+    Args:
+        string: ASCII string which needs to be checked for unique characters
+    Returns:
+        True if string has unique characters False otherwise.
+    """
+    check = [0 for _ in range(8)]
+    for char in string:
+        v = ord(char)
+        # find int bucket which will represent this char
+        idx = int(v / 32)
+        # find the bit in this int bucket which will represent this char
+        shift = v % 32
+
+        if check[idx] & (1 << shift):
+            return False
+        check[idx] |= (1 << shift)
+
+    return True
+
+
+if __name__ == "__main__":
+    str1 = "hello"
+    print(F"'{str1}' has unique characters? :", is_unique(str1))
+    str2 = "norepat"
+    print(F"'{str2}' has unique characters? :", is_unique2(str2))