Easier math for part 2.

2021/6/main2.py

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+# "constants":
+DAYS = 256
+
+# intialize shared data:
+fish_reproducing_on_day = []
+for i in range(0, DAYS + 9):
+    fish_reproducing_on_day.append(0)
+
+# functions:
+def SimulateFish(days_until_next_fish, total_days_left):
+    # # DEBUG(dev):
+    # print('SimulateFish(', days_until_next_fish, ',', total_days_left, ')')
+
+    # If we're past the final date, don't count any more:
+    if(total_days_left - days_until_next_fish <= 0):
+        # add 1 for THIS fish
+        return 1
+
+    total = 0
+    # Add up all the totals of the fish this one is going to spawn
+    for i in range(total_days_left - days_until_next_fish, 0, -7):
+        total += SimulateFish(9, i)
+    # Add this fish, as well
+    total += 1
+
+    # Return grand total from this fish (INCLUDING this fish)
+    return total
+
+def SimulateFishByDay(current_day):
+    fish_reproducing_on_day[current_day + 7] += fish_reproducing_on_day[current_day]
+    fish_reproducing_on_day[current_day + 9] += fish_reproducing_on_day[current_day]
+    return fish_reproducing_on_day[current_day]
+
+#### MAIN EXECUTION ####
+fish = []
+with open('data', 'r') as fp:
+    fish = fp.readline().strip().split(',')
+
+grand_total_1 = 0
+for i in range(0, len(fish)):
+    grand_total_1 += SimulateFish(int(fish[i]), 80)
+
+print(grand_total_1)
+
+
+
+for i in range(0, len(fish)):
+    fish_reproducing_on_day[int(fish[i])] += 1
+
+grand_total_2 = 300 # starting fish count
+for i in range(0, DAYS):
+    print(fish_reproducing_on_day)
+    grand_total_2 += SimulateFishByDay(i)
+print(grand_total_2)
+