Solution to problem 2 in Python

src/Year_2019/P2.py

@@ -0,0 +1,193 @@
+# --- Day 2: 1202 Program Alarm ---
+
+# On the way to your gravity assist around the Moon, your ship computer beeps
+# angrily about a "1202 program alarm". On the radio, an Elf is already
+# explaining how to handle the situation: "Don't worry, that's perfectly
+# norma--" The ship computer bursts into flames.
+
+# You notify the Elves that the computer's magic smoke seems to have escaped.
+# "That computer ran Intcode programs like the gravity assist program it was
+# working on; surely there are enough spare parts up there to build a new
+# Intcode computer!"
+
+# An Intcode program is a list of integers separated by commas (like 1,0,0,3,
+# 99). To run one, start by looking at the first integer (called position 0).
+# Here, you will find an opcode - either 1, 2, or 99. The opcode indicates what
+# to do; for example, 99 means that the program is finished and should
+# immediately halt. Encountering an unknown opcode means something went wrong.
+
+# Opcode 1 adds together numbers read from two positions and stores the result
+# in a third position. The three integers immediately after the opcode tell you
+# these three positions - the first two indicate the positions from which you
+# should read the input values, and the third indicates the position at which
+# the output should be stored.
+
+# For example, if your Intcode computer encounters 1,10,20,30, it should read
+# the values at positions 10 and 20, add those values, and then overwrite the
+# value at position 30 with their sum.
+
+# Opcode 2 works exactly like opcode 1, except it multiplies the two inputs
+# instead of adding them. Again, the three integers after the opcode indicate
+# where the inputs and outputs are, not their values.
+
+# Once you're done processing an opcode, move to the next one by stepping
+# forward 4 positions.
+
+# For example, suppose you have the following program:
+
+# 1,9,10,3,2,3,11,0,99,30,40,50
+
+# For the purposes of illustration, here is the same program split into
+# multiple lines:
+
+# 1,9,10,3,
+# 2,3,11,0,
+# 99,
+# 30,40,50
+
+# The first four integers, 1,9,10,3, are at positions 0, 1, 2, and 3. Together,
+# they represent the first opcode (1, addition), the positions of the two
+# inputs (9 and 10), and the position of the output (3). To handle this opcode,
+# you first need to get the values at the input positions: position 9 contains
+# 30, and position 10 contains 40. Add these numbers together to get 70. Then,
+# store this value at the output position; here, the output position (3) is at
+# position 3, so it overwrites itself. Afterward, the program looks like this:
+
+# 1,9,10,70,
+# 2,3,11,0,
+# 99,
+# 30,40,50
+
+# Step forward 4 positions to reach the next opcode, 2. This opcode works just
+# like the previous, but it multiplies instead of adding. The inputs are at
+# positions 3 and 11; these positions contain 70 and 50 respectively.
+# Multiplying these produces 3500; this is stored at position 0:
+
+# 3500,9,10,70,
+# 2,3,11,0,
+# 99,
+# 30,40,50
+
+# Stepping forward 4 more positions arrives at opcode 99, halting the program.
+
+# Here are the initial and final states of a few more small programs:
+
+#     1,0,0,0,99 becomes 2,0,0,0,99 (1 + 1 = 2).
+#     2,3,0,3,99 becomes 2,3,0,6,99 (3 * 2 = 6).
+#     2,4,4,5,99,0 becomes 2,4,4,5,99,9801 (99 * 99 = 9801).
+#     1,1,1,4,99,5,6,0,99 becomes 30,1,1,4,2,5,6,0,99.
+
+# Once you have a working computer, the first step is to restore the gravity
+# assist program (your puzzle input) to the "1202 program alarm" state it had
+# just before the last computer caught fire. To do this, before running the
+# program, replace position 1 with the value 12 and replace position 2 with the
+# value 2. What value is left at position 0 after the program halts?
+
+
+with open("files/P2.txt") as f:
+    data = [int(number) for number in f.read().strip().split(",")]
+
+
+def part_1() -> None:
+    # before starting
+    _data = data.copy()
+    _data[1] = 12
+    _data[2] = 2
+
+    for i in range(len(_data) // 4):
+        opcode = _data[4 * i]
+        i1 = _data[4 * i + 1]
+        i2 = _data[4 * i + 2]
+        o3 = _data[4 * i + 3]
+        if opcode == 1:
+            res = _data[i1] + _data[i2]
+            _data[o3] = res
+        elif opcode == 2:
+            res = _data[i1] * _data[i2]
+            _data[o3] = res
+        elif opcode == 99:
+            break
+
+    print(f"First value of the instructions is {_data[0]}")
+
+
+# --- Part Two ---
+
+# "Good, the new computer seems to be working correctly! Keep it nearby during
+# this mission - you'll probably use it again. Real Intcode computers support
+# many more features than your new one, but we'll let you know what they are as
+# you need them."
+
+# "However, your current priority should be to complete your gravity assist
+# around the Moon. For this mission to succeed, we should settle on some
+# terminology for the parts you've already built."
+
+# Intcode programs are given as a list of integers; these values are used as
+# the initial state for the computer's memory. When you run an Intcode program,
+# make sure to start by initializing memory to the program's values. A position
+# in memory is called an address (for example, the first value in memory is at
+# "address 0").
+
+# Opcodes (like 1, 2, or 99) mark the beginning of an instruction. The values
+# used immediately after an opcode, if any, are called the instruction's
+# parameters. For example, in the instruction 1,2,3,4, 1 is the opcode; 2, 3,
+# and 4 are the parameters. The instruction 99 contains only an opcode and has
+# no parameters.
+
+# The address of the current instruction is called the instruction pointer; it
+# starts at 0. After an instruction finishes, the instruction pointer increases
+# by the number of values in the instruction; until you add more instructions
+# to the computer, this is always 4 (1 opcode + 3 parameters) for the add and
+# multiply instructions. (The halt instruction would increase the instruction
+# pointer by 1, but it halts the program instead.)
+
+# "With terminology out of the way, we're ready to proceed. To complete the
+# gravity assist, you need to determine what pair of inputs produces the output
+# 19690720."
+
+# The inputs should still be provided to the program by replacing the values at
+# addresses 1 and 2, just like before. In this program, the value placed in
+# address 1 is called the noun, and the value placed in address 2 is called the
+# verb. Each of the two input values will be between 0 and 99, inclusive.
+
+# Once the program has halted, its output is available at address 0, also just
+# like before. Each time you try a pair of inputs, make sure you first reset
+# the computer's memory to the values in the program (your puzzle input) - in
+# other words, don't reuse memory from a previous attempt.
+
+# Find the input noun and verb that cause the program to produce the output
+# 19690720. What is 100 * noun + verb? (For example, if noun=12 and verb=2, the
+# answer would be 1202.)
+
+# from copy import copy
+
+
+def part_2() -> None:
+    for noun in range(100):
+        for verb in range(100):
+            # before starting
+            _data = data.copy()
+            _data[1] = noun
+            _data[2] = verb
+
+            for i in range(len(_data) // 4):
+                opcode = _data[4 * i]
+                i1 = _data[4 * i + 1]
+                i2 = _data[4 * i + 2]
+                o3 = _data[4 * i + 3]
+                if opcode == 1:
+                    res = _data[i1] + _data[i2]
+                    _data[o3] = res
+                elif opcode == 2:
+                    res = _data[i1] * _data[i2]
+                    _data[o3] = res
+                elif opcode == 99:
+                    break
+
+            if _data[0] == 19690720:
+                print(f"The final result is {100*noun+verb}")
+
+
+if __name__ == "__main__":
+    part_1()
+    part_2()