day5-take3.py

# Read the input from the file and parse it
with open("input.txt") as f:
    lines = f.readlines()

# Create the initial stacks of crates by splitting the first three lines of the input
stack1 = list(lines[0].strip())
stack2 = list(lines[1].strip())
stack3 = list(lines[2].strip())

# Define the movement steps as a list of tuples, where each tuple
# contains the source stack, the destination stack, and the number of crates to move
steps = []
for line in lines[4:]:
    # Skip empty lines
    if not line.strip():
        continue

    # Strip leading and trailing whitespace from the line, then split it into individual words
    # and convert the source and destination stacks to integers
    words = line.strip().split()
    source = int(words[1])
    dest = int(words[3])

    # Convert the number of crates to move to an integer and append it to the tuple
    print(words)
    num_crates = int(words[4])
    step = (source, dest, num_crates)
    steps.append(step)

# Loop through the steps and simulate the movement of the crates
for step in steps:
    # Unpack the source stack, destination stack, and number of crates from the tuple
    source, dest, num_crates = step
    
    # Move the crates from the source stack to the destination stack
    for i in range(num_crates):
        if source == 1:
            # Move a crate from stack1 to the destination stack
            crate = stack1.pop()
            if dest == 2:
                stack2.append(crate)
            elif dest == 3:
                stack3.append(crate)
        elif source == 2:
            # Move a crate from stack2 to the destination stack
            crate = stack2.pop()
            if dest == 1:
                stack1.append(crate)
            elif dest == 3:
                stack3.append(crate)
        elif source == 3:
            # Move a crate from stack3 to the destination stack
            crate = stack3.pop()
            if dest == 1:
                stack1.append(crate)
            elif dest == 2:
                stack2.append(crate)

# Determine the top crate on each stack
top1 = stack1[-1]
top2 = stack2[-1]
top3 = stack3[-1]