6

#############################################################
# FILE : balanced_brackets.py
# WRITER : arthur_oxenhorn , arthuro ,
# EXERCISE : intro2cs ex6
# DESCRIPTION:
# palindrome
#############################################################
def is_palindrome_1(s):
    if len(s) < 2:
        return True
    if s[0] != s[len(s)-1]:
        return False
    return is_palindrome_1(s[1:-1])

def is_palindrome_2(s, i, j):
    if s[i] != s[j]:
        return False
    if j-i < 2:
        return True
    return is_palindrome_2(s, i+1, j-1)
#############################################################
# FILE : balanced_brackets.py
# WRITER : arthur_oxenhorn , arthuro ,
# EXERCISE : intro2cs ex6
# DESCRIPTION:
# strings and brackets.
#############################################################
def is_balanced(s):
    right_counter = 0 #(
    left_counter = 0 #)
    b = False
    for i in range(len(s)):
        if s[i] == '(':
            b = True
            right_counter = right_counter + 1
        if (s[i] == ')'):
            left_counter = left_counter + 1
            if right_counter == left_counter:
                b = True
            else:
                b = False
    if left_counter != right_counter:
        return False
    return b

def match_brackets(s):
    if is_balanced(s) == False:
        return[]

    index_list = [] #indexes of brackets
    index_list2 = [] #of letters


    for i in range(len(s)):
        if s[i] == ")" or s[i] == "(":
            index_list.append(i)
        else:
            index_list2.append(i)

    a = [0]* len(index_list)
    b = newlst(index_list, 0, len(index_list)-1,a)
    nlst = [0]* (len(s))
    for i in range(len(index_list2)):
        nlst[index_list2[i]] = 0

    for i in range(len(index_list)):
        nlst[index_list[i]] = b[i]

    return nlst


def newlst(lst,i, j,a):
    if len(lst) == 0 or j==-1:
        return a
    a[i] = lst[j] - lst[i]
    a[j] = lst[i] - lst[j]

    return (newlst(lst, i+1, j-1, a))

#############################################################
# FILE : balanced_brackets.py
# WRITER : arthur_oxenhorn , arthuro ,
# EXERCISE : intro2cs ex6
# DESCRIPTION:
# turtle draws y tree
#############################################################
import turtle

def draw_tree(length):
    if length < 10:
        return
    #else
    turtle.down()
    turtle.forward(length)
    turtle.left(30)
    draw_tree(length * 0.6)
    turtle.right(60)
    draw_tree(length * 0.6)
    turtle.left(30)
    turtle.backward(length)
    return