instructions and a possible solution for String to Integer (Atoi) problem

0008/README.md

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+## String to Integer
+
+* https://leetcode.com/problems/string-to-integer-atoi/description/
+
+* Implement atoi to convert a string to an integer.
+
+*Hint:* Carefully consider all possible input cases. If you want a challenge, please do not see below and ask yourself what are the possible input cases.
+
+*Notes:* 
+* It is intended for this problem to be specified vaguely (ie, no given input specs). You are responsible to gather all the input requirements up front.
+
+
+
+### Requirements for atoi:
+* The function first discards as many whitespace characters as necessary until the first non-whitespace character is found. 
+* Then, starting from this character, takes an optional initial plus or minus sign followed by as many numerical digits as possible, and interprets them as a numerical value.
+* The string can contain additional characters after those that form the integral number, which are ignored and have no effect on the behavior of this function.
+* If the first sequence of non-whitespace characters in str is not a valid integral number, or if no such sequence exists because either str is empty or it contains only whitespace characters, no conversion is performed.
+* If no valid conversion could be performed, a zero value is returned. If the correct value is out of the range of representable values, `INT_MAX (2147483647)` or `INT_MIN (-2147483648)` is returned.
+
+## Possible Solution
+You can examine a possible solution in `string_to_integer.py`

0008/string_to_integer.py

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+class Solution(object):
+    INT_MAX = 2147483647
+    INT_MIN = -2147483648
+
+    def convert_string_to_int(self, string_input_value):
+        length = len(string_input_value)
+
+        for i in range(length):
+            if string_input_value[0] == ' ':
+                string_input_value = string_input_value[1:]
+            else:
+                break
+
+        num = 0
+        pos = True
+        for i in range(len(string_input_value)):
+            if i == 0 and string_input_value[i] == '+':
+                pos = True
+            elif i == 0 and string_input_value[i] == '-':
+                pos = False
+            elif not ('0' <= string_input_value[i] <= '9'):
+                if pos:
+                    return num
+                else:
+                    (-1) * num
+            else:
+                num = num * 10 + int(string_input_value[i])
+                if num > self.INT_MAX and pos:
+                    return self.INT_MAX
+                elif num > self.INT_MIN and not pos:
+                    return self.INT_MIN
+
+        if pos:
+            return num
+        else:
+            return (-1) * num