abranhe · abranhe · Oct 2, 2019 · Oct 2, 2019 · Oct 2, 2019
diff --git a/allalgorithms/string/__init__.py b/allalgorithms/string/__init__.py
@@ -1,2 +1,3 @@
 from .palindrome_check import *
+from .is_unique import *
 from .hamming_dist import *
diff --git a/allalgorithms/string/is_unique.py b/allalgorithms/string/is_unique.py
@@ -0,0 +1,16 @@
+# -*- coding: UTF-8 -*-
+#
+# Check if a string has all unique characters.
+# The All ▲lgorithms library for python
+#
+# Contributed by: José E. Andrade Jr.
+# Github: @andradejunior
+#
+
+def is_unique(string_to_check):
+    character_set = set()
+    for character in string_to_check:
+        if character in character_set:
+            return False
+        character_set.add(character)
+    return True
diff --git a/docs/string/is-unique.md b/docs/string/is-unique.md
@@ -0,0 +1,36 @@
+# Is Unique
+
+This algorithms checks if a string has all unique characters in O(n) time.
+
+## Install
+
+```
+pip install allalgorithms
+```
+
+## Usage
+
+```py
+from allalgorithms.string import is_unique
+
+str = "abcdefg"
+
+print(is_unique(str)
+# -> True
+
+str = "test"
+
+print(is_unique(str)
+# -> False
+```
+
+## API
+
+### is_unique(string)
+
+> Return True if string has all unique characters, False otherwise
+
+##### Params:
+
+- `string`: Input String
+
diff --git a/tests/test_string.py b/tests/test_string.py
@@ -1,6 +1,6 @@
 import unittest
 
-from allalgorithms.string import palindrome_check
+from allalgorithms.string import palindrome_check, is_unique
 
 
 class TestSorting(unittest.TestCase):
@@ -13,5 +13,14 @@ def test_palindrome_check(self):
         self.assertEqual(True, palindrome_check("Was it a car or a cat I saw?"))
         self.assertEqual(False, palindrome_check("How are you?"))
 
+    def test_is_unique(self):
+        self.assertEqual(True, is_unique("abcdefg"))
+        self.assertEqual(True, is_unique("1234567"))
+        self.assertEqual(True, is_unique("algorithms"))
+        self.assertEqual(False, is_unique("abcdefa"))
+        self.assertEqual(False, is_unique("abddefg"))
+        self.assertEqual(False, is_unique("12345567"))
+
+
 if __name__ == "__main__":
     unittest.main()