dailylog 02-02-21

# FROM HERE https://leetcode.com/problems/longest-valid-parentheses/discuss/1030761/
# ... Python-Simple-Solutions-or-DP-and-Stack-One-pass
import unittest
def longestValidParentheses(my_string):

# INITIALIZES RESULT VAR
# INITIALIZES A STACK
    result = 0
    my_stack = []

# LOOPS THROUGH EACH PAREN IN STRING, BY ID NUMBER
# **** BY ID NUMBER ****
    for idx in range(len(my_string)):

# If -- the character at the IDX we are iterating over is a "("
# Add the IDX to our stack

        if my_string[idx] == '(':
            my_stack.append(idx)

# If --  STACK exists, AND the last IDX in STACK
# corresponds to a '(' in STRING
# Remove the last IDX from the stack
# Create a LAST POSITION variable
# it becomes the last IDX in STACK (if stack exists)
# Create a CURRENT LENGTH variable
# It becomes the currend IDX minus Last Position
# Create a RESULT variable
# This simply takes the max between result and CURRENT LENGTH

        elif my_stack and my_string[my_stack[-1]] == '(':
            my_stack.pop()
            lastPos = my_stack[-1] if my_stack else -1
            curLen = idx - lastPos
            result = max(result, curLen)

# Else -- Simply add the idx to the stack
        else:
            my_stack.append(idx)
    return result

class Test(unittest.TestCase):
    '''Test Cases'''
    data = [
        ("(()", 2),
        (")()())", 4),
        ("()(()", 2)
    ]
    def test_paren_strings(self):
        for [paren_string, expected] in self.data:
            actual = longestValidParentheses(paren_string)
            self.assertEqual(actual, expected)

unittest.main(argv=[''], verbosity=2, exit=False)