# read input into python
with open("day01_input.txt", "r") as f:
    lines_input = f.readlines() 
    # lines_input is a list of strings, 
    # each string is one line in the input.txt
    lines = [int(a) for a in lines_input]
    # lines is list of list of integer.
    # here we used `list comprehension`. will discuss it later.

# example of for loop
# suppose we have 3 lists: part1, part2, part3, all have same size of 10
# we want to add first element of all 3 lists, 
# second elements of all 3 lists, etc

output = [] # we need somewhere to put the outputs
for i in range(10):
    o = part1[i] + part2[i] + part3[i]
    output.append(o)
    
# method2: use list comprehension instead of `for loop`
output = [a+b+c for (a, b, c) in zip(part1, part2, part3)]

# another example of list comprehension
l2 = [a*2 for a in l1]
    

# binary string to integer
b_str = "0b1001" # add "0b" prefix
i_num = int(b_str, 2)

print("{} == {}".format(b_str, i_num))

# use recursive function to solve problem.
# The benefit is that you only think one step.
# and the final step where it stops and return.

# a good tutorial at: https://realpython.com/python-thinking-recursively/

# example function 
def fibonacci_recursive(n):
    print("Calculating F", "(", n, ")", sep="", end=", ")

    # Base case. This is where the function will stop
    if n == 0:
        return 0
    elif n == 1:
        return 1

    # Recursive case
    else:
        # note the parameters are decreasing
        return fibonacci_recursive(n-1) + fibonacci_recursive(n-2)

from heapq import heappush, heappop

# example of heapq. 
# you can use it get point with least loss at this moment.

#   (loss, (y, x))
a = (12, (9, 10))
b = (8, (3, 4))
c = (1, (1, 1))

loss = []
heappush(loss, a)
heappush(loss, b)
print("initialized heap: {}".format(loss))

least_loss = heappop(loss)
print("current least loss: {}".format(least_loss))
print("heap after pop: {}".format(loss))

heappush(loss, c)
print("heap after push c: {}".format(loss))