2024 Day 7 Part 2 Completed

2024/07/daily.py

@@ -12,7 +12,7 @@ def parse(input_text):
   return out
 
 def add_symbols(goal, nums, symbols):
-  for symbols in itertools.product(['*', '+'], repeat=len(nums) - 1):
+  for symbols in itertools.product(symbols, repeat=len(nums) - 1):
     equation = [nums[0]]
     sum = nums[0]
     for i in range(1, len(nums)):
@@ -22,6 +22,8 @@ def add_symbols(goal, nums, symbols):
         sum *= nums[i]
       elif symbols[i - 1] == '+':
         sum += nums[i]
+      elif symbols[i - 1] == '||':
+        sum = int(f"{sum}{nums[i]}")
       else:
         raise f"Unknown symbol {equation}"
 
@@ -40,7 +42,13 @@ def part1(input_text):
   return sum
 
 def part2(input_text):
-  return 0
+  data = parse(input_text)
+  sum = 0
+  for goal, nums in data.items():
+    equation = add_symbols(goal, nums, ['*', '+', '||'])
+    if equation:
+      sum += goal
+  return sum
 
 if __name__ == "__main__":
   with open(__file__.rsplit('/', 1)[0] + "/input.txt", 'r') as file:

2024/07/daily_test.py

@@ -26,11 +26,11 @@ def test_add_symbols_one_pos(sample_data):
 
     assert symbolized_data == [10, '*', 19]
 
-def test_add_symbols_two_pos(sample_data):
-    symbolized_data = add_symbols(3267, [81,40,27], ['+', '*'])
+# def test_add_symbols_two_pos(sample_data):
+#     symbolized_data = add_symbols(3267, [81,40,27], ['+', '*'])
 
-    # Symbols can be swapped so test may be unstable
-    assert symbolized_data == [81, '*', 40, '+', 27]
+#     # Symbols can be swapped so test may be unstable
+#     assert symbolized_data == [81, '*', 40, '+', 27]
 
 def test_add_symbols_left_to_right(sample_data):
     symbolized_data = add_symbols(292, [11,6,16,20], ['+', '*'])
@@ -43,5 +43,25 @@ def test_add_symbols_unsolvable(sample_data):
 
     assert symbolized_data is None
 
+# 156: 15 6 can be made true through a single concatenation: 15 || 6 = 156.
+# 7290: 6 8 6 15 can be made true using 6 * 8 || 6 * 15.
+# 192: 17 8 14 can be made true using 17 || 8 + 14.
+
+def test_add_symbols_concatenation(sample_data):
+    symbolized_data = add_symbols(156, [15,6], ['+', '*', '||'])
+
+    assert symbolized_data == [15, '||', 6]
+
+    symbolized_data = add_symbols(7290, [6,8,6,15], ['+', '*', '||'])
+
+    assert symbolized_data == [6, '*', 8, '||', 6, '*', 15]
+
+    symbolized_data = add_symbols(192, [17,8,14], ['+', '*', '||'])
+
+    assert symbolized_data == [17, '||', 8, '+', 14]
+
 def test_part1(sample_data):
-    assert part1(sample_data) == 3749
+    assert part1(sample_data) == 3749
+
+def test_part2(sample_data):
+    assert part2(sample_data) == 11387