Day 3

day03-1.py

+from helpers import debug, load_input
+
+def is_digit(n):
+    try:
+        m = int(n)
+    except ValueError:
+        return False
+    return True
+
+class InputNumber:
+    def __init__(self, number, start_pos, end_pos, line):
+        self.number = number
+        self.start_pos = start_pos
+        self.end_pos = end_pos
+        self.line = line
+
+    def _is_symbol(self, char):
+        return (char != "." and not is_digit(char))
+
+    def _check_up(self, input):
+        if self.line == 0:
+            return False
+        cur_line = input[self.line - 1]
+        for i in range(max(0, self.start_pos-1), min(len(cur_line)-1, self.end_pos+2)):
+            char = cur_line[i]
+            if self._is_symbol(char):
+                debug(f"Found symbol next to {self.number} at line {self.line-1}: {i}")
+                return True
+        return False
+    
+    def _check_down(self, input):
+        if self.line == len(input)-1:
+            return False
+        cur_line = input[self.line + 1]
+        for i in range(max(0, self.start_pos-1), min(len(cur_line)-1, self.end_pos+2)):
+            char = cur_line[i]
+            if self._is_symbol(char):
+                debug(f"Found symbol next to {self.number} at line {self.line+1}: {i}")
+                return True
+        return False
+    
+    def _check_left(self, input):
+        if self.start_pos == 0:
+            debug("Already at the left-hand side of the line")
+            return False
+        if self._is_symbol(input[self.line][self.start_pos-1]):
+            debug(f"Found symbol next to {self.number} at line {self.line}: {self.start_pos-1}")
+            return True
+        return False
+
+    def _check_right(self, input):
+        if self.end_pos == len(input[0]) - 1:
+            debug("Already at the right-hand side of the line")
+            return False
+        if self._is_symbol(input[self.line][self.end_pos+1]):
+            debug(f"Found symbol next to {self.number} at line {self.line}: {self.end_pos+1}")
+            return True
+        return False
+    
+    def is_part_number(self, input):
+        return (
+            self._check_up(input)
+            or self._check_down(input)
+            or self._check_left(input)
+            or self._check_right(input)
+        )
+        
+
+def main():
+    lines = load_input(3)
+    # Input is lines of periods (.), numbers (0-9), and symbols 
+    # (anything that isn't a period or number)
+    # Any number adjacent (horizontally, vertically, diagonally)
+    # to a symbol is a part number. Get the sum of the part numbers.
+    max_len = len(lines[0]) # all lines are the same length
+    positions = []
+    for j, line in enumerate(lines):
+        i = 0
+        while i < max_len:
+            if is_digit(line[i]):
+                current_number = ""
+                start_pos = i
+                while i < max_len and is_digit(line[i]):
+                    current_number += f"{line[i]}"
+                    i += 1
+                end_pos = i
+                input_number = InputNumber(
+                    number = int(current_number),
+                    start_pos = start_pos,
+                    end_pos = end_pos-1, # i is one greater than the end of the number
+                    line = j
+                )
+                positions.append(input_number)
+                debug(f"Found {input_number.number} at line {input_number.line} ({input_number.start_pos}, {input_number.end_pos})")
+            i += 1
+    # Now I have a list of the positions of all the numbers in the input.
+    part_numbers = []
+    for p in positions:
+        if p.is_part_number(lines):
+            part_numbers.append(p.number)
+    
+    print(sum(part_numbers))
+
+if __name__ == "__main__":
+    main()

day03-2.py

+from helpers import debug, load_input
+
+def is_digit(n):
+    try:
+        m = int(n)
+    except ValueError:
+        return False
+    return True
+
+def is_star(n):
+    return n == "*"
+
+input_numbers = []
+stars = []
+
+class InputNumber:
+    def __init__(self, number, start_pos, end_pos, line):
+        self.number = number
+        self.start_pos = start_pos
+        self.end_pos = end_pos
+        self.line = line
+
+    def _is_symbol(self, char):
+        return (char != "." and not is_digit(char))
+
+    def _check_up(self, input):
+        if self.line == 0:
+            return False
+        cur_line = input[self.line - 1]
+        for i in range(max(0, self.start_pos-1), min(len(cur_line)-1, self.end_pos+2)):
+            char = cur_line[i]
+            if self._is_symbol(char):
+                debug(f"Found symbol next to {self.number} at line {self.line-1}: {i}")
+                return True
+        return False
+    
+    def _check_down(self, input):
+        if self.line == len(input)-1:
+            return False
+        cur_line = input[self.line + 1]
+        for i in range(max(0, self.start_pos-1), min(len(cur_line)-1, self.end_pos+2)):
+            char = cur_line[i]
+            if self._is_symbol(char):
+                debug(f"Found symbol next to {self.number} at line {self.line+1}: {i}")
+                return True
+        return False
+    
+    def _check_left(self, input):
+        if self.start_pos == 0:
+            debug("Already at the left-hand side of the line")
+            return False
+        if self._is_symbol(input[self.line][self.start_pos-1]):
+            debug(f"Found symbol next to {self.number} at line {self.line}: {self.start_pos-1}")
+            return True
+        return False
+
+    def _check_right(self, input):
+        if self.end_pos == len(input[0]) - 1:
+            debug("Already at the right-hand side of the line")
+            return False
+        if self._is_symbol(input[self.line][self.end_pos+1]):
+            debug(f"Found symbol next to {self.number} at line {self.line}: {self.end_pos+1}")
+            return True
+        return False
+    
+    def is_part_number(self, input):
+        return (
+            self._check_up(input)
+            or self._check_down(input)
+            or self._check_left(input)
+            or self._check_right(input)
+        )
+    
+    def thats_me(self, line, pos):
+        return self.line == line and pos in range(self.start_pos, self.end_pos+1)
+
+class Star:
+    def __init__(self, line, pos):
+        self.line = line
+        self.pos = pos
+        self.adjacent_numbers = []
+
+    def _check_up(self, input):
+        if self.line == 0:
+            debug("Already at the top")
+            return False
+        found_one = False
+        for i in range(self.pos-1, self.pos+2):
+            debug(f"Checking {self.line-1}:{i}")
+            char = input[self.line-1][i]
+            if is_digit(char):
+                target_number = [number for number in input_numbers if number.thats_me(self.line-1, i)][0]
+                if target_number not in self.adjacent_numbers:
+                    self.adjacent_numbers.append(target_number)
+                found_one = True
+        return found_one
+    
+    def _check_down(self, input):
+        if self.line == len(input) - 1:
+            debug("Already at the bottom")
+            return False
+        found_one = False
+        for i in range(self.pos-1, self.pos+2):
+            debug(f"Checking {self.line+1}:{i}")
+            char = input[self.line+1][i]
+            if is_digit(char):
+                target_number = [number for number in input_numbers if number.thats_me(self.line+1, i)][0]
+                if target_number not in self.adjacent_numbers:
+                    self.adjacent_numbers.append(target_number)
+                found_one = True
+        return found_one
+    
+    def _check_left(self, input):
+        if self.pos == 0:
+            debug ("Already at the left side")
+            return False
+        debug(f"Checking {self.line}:{self.pos-1}")
+        char = input[self.line][self.pos-1]
+        if is_digit(char):
+            target_number = [number for number in input_numbers if number.thats_me(self.line, self.pos-1)][0]
+            if target_number not in self.adjacent_numbers:
+                self.adjacent_numbers.append(target_number)
+            return True
+        return False
+    
+    def _check_right(self, input):
+        if self.pos == len(input[0]) - 1:
+            debug ("Already at the right side")
+            return False
+        debug(f"Checking {self.line}:{self.pos+1}")
+        char = input[self.line][self.pos+1]
+        if is_digit(char):
+            target_number = [number for number in input_numbers if number.thats_me(self.line, self.pos+1)][0]
+            if target_number not in self.adjacent_numbers:
+                self.adjacent_numbers.append(target_number)
+            return True
+        return False
+    
+    def _is_gear(self, input):
+        self._check_up(input)
+        self._check_down(input)
+        self._check_left(input)
+        self._check_right(input)
+        l_adj = len(self.adjacent_numbers)
+        n_adj = [number.number for number in self.adjacent_numbers]
+        debug(f"Star at {self.line}:{self.pos} has {l_adj} adjacent number{'s' if l_adj > 1 else ''}: {n_adj}")
+        return len(self.adjacent_numbers) == 2
+    
+    def gear_value(self, input):
+        if self._is_gear(input):
+            return self.adjacent_numbers[0].number * self.adjacent_numbers[1].number
+        return 0
+
+def main():
+    lines = load_input(3)
+    # Input is lines of periods (.), numbers (0-9), and symbols 
+    # (anything that isn't a period or number)
+    # Any number adjacent (horizontally, vertically, diagonally)
+    # to a symbol is a part number. Get the sum of the part numbers.
+    max_len = len(lines[0]) # all lines are the same length
+    for j, line in enumerate(lines):
+        i = 0
+        while i < max_len:
+            if is_star(line[i]):
+                star = Star(
+                    line=j,
+                    pos=i
+                )
+                stars.append(star)
+                # debug(f"Found a star at {star.line}:{star.pos}")
+            elif is_digit(line[i]):
+                current_number = ""
+                start_pos = i
+                while i < max_len and is_digit(line[i]):
+                    current_number += f"{line[i]}"
+                    i += 1
+                if i < max_len and is_star(line[i]):
+                    star = Star(
+                        line=j,
+                        pos=i
+                    )
+                    stars.append(star)
+                    # debug(f"Found a star next to a number at {star.line}:{star.pos}")
+                end_pos = i
+                input_number = InputNumber(
+                    number = int(current_number),
+                    start_pos = start_pos,
+                    end_pos = end_pos-1, # i is one greater than the end of the number
+                    line = j
+                )
+                input_numbers.append(input_number)
+                # debug(f"Found {input_number.number} at line {input_number.line} ({input_number.start_pos}, {input_number.end_pos})")
+            i += 1
+    # Now I have a list of the positions of all the numbers and stars in the input.
+    gear_values = []
+    for s in stars:
+        gear_values.append(s.gear_value(lines))
+    
+    print(sum(gear_values))
+
+if __name__ == "__main__":
+    main()