airwrk_submission_ruhshan

## solution to problem 1
def is_palindrome(n):
    if n < 0:
        return False
    
    s = str(n)

    flag = 0

    for c in s[:len(s)/2]:
        flag+=int(c)

    middle = len(s)/2 if len(s)%2 == 0 else 1+len(s)/2

    for c in s[middle:]:
        flag -= int(c)
    
    if flag == 0:
        return True

    return False


# solution to problem 2

from collections import defaultdict

def find_unique_element(arr):
    count = defaultdict(int)
    
    for element in arr:
        count[element]+=1
    
    for element, occurance in count.items():
        if occurance == 1:
            return element


# solution to problem 3

def check_changes(bills):
    current_total = 0

    for bill in bills:
        if bill > 5:
            change = bill - 5
            if change > current_total:
                return False
            else:
                current_total-=change
        current_total+=5
    
    return True