3b.py

#Advent of code 2021
# 12/05/21 day 3b
# Joe McFarland
# import sys
# import re
import copy

filename = "data3.txt"

file = open(filename)
filestr = file.read()
a_list = filestr.split("\n")
maxrows = len(a_list)
#print(a_list)
maxcols = len(a_list[0])

def findDiag( isOxygen ):
    diag = None
    current_list = copy.deepcopy(a_list)
    for col in range(maxcols):
        zero_bits = one_bits = 0
        for row in current_list:
            if row[col] == "0":
                zero_bits += 1
            elif row[col] == "1":
                one_bits += 1
        if ( isOxygen ):
            if one_bits >= zero_bits:
                common = 1             # most common
            else:
                common = 0
        else:
            if one_bits < zero_bits:
                common = 1             # least common
            else:
                common = 0
        new_list = []
        for row in current_list:
            if row[col] == str(common):
                new_list.append(row)
        #print(f"new_list(col={col}):\n{new_list}")
        if len(new_list) == 1:
            print(f"found entry, {new_list}")
            #found_val = new_list[0]
            diag = int(new_list[0],2)
            break
        current_list = copy.deepcopy(new_list)
    print(f"diag = {diag}")
    return diag

ogen = findDiag( True )
co2 = findDiag( False )
print(f"mul = {ogen*co2}")