feat(strings): string to integer

Author: BrianLusina

pystrings/strtoint/README.md

@@ -0,0 +1,8 @@
+# String to Integer
+
+You are given some numeric string as input. You have to convert the string you are given to an integer.
+
+Do not make use of the built-in int function.
+
+Hint:
+123 = 100 + 20 + 3 = 1 * 100 + 2 * 10 + 3 * 1

pystrings/strtoint/__init__.py

@@ -0,0 +1,26 @@
+def str_to_int(input_str: str) -> int:
+    """
+    Converts an input string int an integer
+    Args:
+        input_str(str): input string
+    Returns:
+        int integer representation of the input string
+    """
+    output_int = 0
+
+    if input_str[0] == '-':
+        is_negative = True
+    else:
+        is_negative = False
+
+    str_len = len(input_str)
+    l = str_len - 1 if is_negative else str_len
+    str_to_convert = input_str[1:] if is_negative else input_str
+
+    for index, char in enumerate(str_to_convert):
+        unicode = ord(char) - ord('0')
+        exponent = l - (index + 1)
+        number = unicode * 10**exponent
+        output_int += number
+
+    return output_int *-1 if is_negative else output_int

pystrings/strtoint/test_string_to_int.py

@@ -0,0 +1,57 @@
+import unittest
+from . import str_to_int
+
+
+class StrToIntTestCases(unittest.TestCase):
+    def test_1(self):
+        """should convert '123' to 123"""
+        input_str = "123"
+        expected = 123
+        actual = str_to_int(input_str)
+        self.assertEqual(expected, actual)
+
+    def test_2(self):
+        """should convert '-12332' to -12332"""
+        input_str = "-12332"
+        expected = -12332
+        actual = str_to_int(input_str)
+        self.assertEqual(expected, actual)
+
+    def test_3(self):
+        """should convert '554' to 554"""
+        input_str = "554"
+        expected = 554
+        actual = str_to_int(input_str)
+        self.assertEqual(expected, actual)
+
+    def test_4(self):
+        """should convert '0' to 0"""
+        input_str = "0"
+        expected = 0
+        actual = str_to_int(input_str)
+        self.assertEqual(expected, actual)
+
+    def test_5(self):
+        """should convert '-1293' to -1293"""
+        input_str = "-1293"
+        expected = -1293
+        actual = str_to_int(input_str)
+        self.assertEqual(expected, actual)
+
+    def test_6(self):
+        """should convert '529' to 529"""
+        input_str = "529"
+        expected = 529
+        actual = str_to_int(input_str)
+        self.assertEqual(expected, actual)
+
+    def test_7(self):
+        """should convert '-999' to -999"""
+        input_str = "-999"
+        expected = -999
+        actual = str_to_int(input_str)
+        self.assertEqual(expected, actual)
+
+
+if __name__ == '__main__':
+    unittest.main()