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Today is day 3 of Advent of Code. See my recent post for an explanation.

The challenge today had us reading a ‘map’ with lines showing either “.” for an empty space, or “#” for a tree. We had to figure out how to walk the map and count the number of trees we’d hit, based on different slopes. It was challening, since I stick at arrays and such, but after many tries, I got both parts right!

Part 1’s Code:

# Advent of Code #3 part 2 - Starting at the top-left corner of your map and
# following a slope of right 3 and down 1, how many trees would you encounter?
treecount = 0
clearspace = '.'
tree = '#'
lineCtr = 0
colCnt = 3
with open("c:\\git\\advent-2020\\3.txt", "r") as f:
    map = f.read().splitlines() 
for line in map:
    # example line:  .........#....#.###.........##.
    lineCtr += 1
    if lineCtr == 1:
        continue
    if colCnt >= 31:
        print("wrapping...")
        colCnt = colCnt - 31
    thisChar = line[colCnt]
    if thisChar == tree:
        treecount += 1
    colCnt += 3
    #if lineCtr >= 12:
    #    break
    
print("There are " + str(len(map)) + " lines on the map, of which, " + str(treecount) + " have trees in the path.")

Part 2’s Code:

# Advent of Code #3 part 2 - What do you get if you multiply together the number of trees
# encountered on each of the listed slopes?
report = ''
with open("c:\\git\\advent-2020\\3.txt", "r") as f:
    map = f.read().splitlines()
def addToReport(value):
    global report
    report += value + "\n"
def getTrees(down, right):
    lineCtr = 1
    colCnt = right
    treecount = 0
    for line in map:
        # example line:  .........#....#.###.........##.
        addToReport(str(lineCtr) + "     " + line)
        if (lineCtr == 1) or (down == 2 and lineCtr == 2):
            lineCtr += 1
            continue
        if (down == 2) and (lineCtr % 2 == 0):
            lineCtr += 1
            continue
        if colCnt >= 31:
            colCnt = colCnt - 31
        thisChar = line[colCnt]
        if thisChar == '#':
            treecount += 1
        addToReport("thisChar =" + thisChar + "  treecount = " + str(treecount) + "  colCnt = " + str(colCnt))
        colCnt += right
        lineCtr += 1
    print ("trees in loop (" + str(right) + "," + str(down) + ")= " + str(treecount))
    return treecount
treesInAllLoops = getTrees(1,1) * getTrees(1,3) * getTrees(1,5) * getTrees(1,7) * getTrees(2,1)
fl = open("3-report.txt", "w")
fl.write(report)
fl.close()
print("There are " + str(treesInAllLoops) + " trees in all paths.")

Cheers!