added is_contains_unique_chars() (#5701)

* added is_contains_unique_chars()

* added is_contains_unique_chars()

* added stackoverflow reference

strings/is_contains_unique_chars.py

@@ -0,0 +1,31 @@
+def is_contains_unique_chars(input_str: str) -> bool:
+    """
+    Check if all characters in the string is unique or not.
+    >>> is_contains_unique_chars("I_love.py")
+    True
+    >>> is_contains_unique_chars("I don't love Python")
+    False
+
+    Time complexity: O(n)
+    Space compexity: O(1) 19320 bytes as we are having 144697 characters in unicode
+    """
+
+    # Each bit will represent each unicode character
+    # For example 65th bit representing 'A'
+    # https://stackoverflow.com/a/12811293
+    bitmap = 0
+    for ch in input_str:
+        ch_unicode = ord(ch)
+        ch_bit_index_on = pow(2, ch_unicode)
+
+        # If we already turned on bit for current character's unicode
+        if bitmap >> ch_unicode & 1 == 1:
+            return False
+        bitmap |= ch_bit_index_on
+    return True
+
+
+if __name__ == "__main__":
+    import doctest
+
+    doctest.testmod()