C first intcode problem

c/2019/2/1202_program_alarm.c

@@ -0,0 +1,36 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <stdbool.h>
+
+#include "../../lib/intcode.h"
+
+#define EXPECTED_OUTPUT 19690720
+
+int main() {
+  ic_load_rom_from_input();
+
+  IC *c = ic_new_computer();
+  ic_poke(c, 1, 12);
+  ic_poke(c, 2, 2);
+  ic_run(c);
+
+  printf("Part 1: %d\n", ic_peek(c, 0));
+
+  int noun, verb;
+  for (noun = 0; noun < 100; noun++) {
+    for (verb = 0; verb < 100; verb++) {
+      ic_reset(c);
+      ic_poke(c, 1, noun);
+      ic_poke(c, 2, verb);
+      ic_run(c);
+      if (ic_peek(c, 0) == EXPECTED_OUTPUT) goto done;
+    }
+  }
+ done:
+
+  printf("Part 2: %d\n", noun * 100 + verb);
+  
+  aoc_free();
+  return 0;
+}

c/lib/intcode.h

@@ -0,0 +1,109 @@
+#include <stdbool.h>
+#include "./aoc.h"
+
+#define ROM_LENGTH 1000
+
+int rom[ROM_LENGTH];
+int rom_count;
+
+typedef struct IC {
+  int *rom;
+  int *data;
+  int program_counter;
+  bool halted;
+} IC;
+
+int ic_peek(IC *c, int address) {
+  return c->data[address];
+}
+
+void ic_poke(IC *c, int address, int value) {
+  c->data[address] = value;
+}
+
+int ic_read(IC *c) {
+  return ic_peek(c, c->program_counter++);
+}
+
+void ic_write(IC *c, int value) {
+  ic_poke(c, ic_peek(c, c->program_counter++), value);
+}
+
+void ic_halt(IC *c) {
+  c->halted = true;
+}
+
+void ic_instruction_add(IC *c) {
+  int x = ic_read(c);
+  int y = ic_read(c);
+  ic_write(c, ic_peek(c, x) + ic_peek(c, y));
+}
+
+void ic_instruction_multiply(IC *c) {
+  int x = ic_read(c);
+  int y = ic_read(c);
+  ic_write(c, ic_peek(c, x) * ic_peek(c, y));
+}
+
+void ic_instruction_halt(IC *c) {
+  ic_halt(c);
+}
+
+int ic_execute_instruction(IC *c) {
+  int opcode = ic_read(c);
+  switch(opcode) {
+  case 1:
+    ic_instruction_add(c);
+    break;
+  case 2:
+    ic_instruction_multiply(c);
+    break;
+  case 99:
+    ic_instruction_halt(c);
+    break;
+  default:
+    printf("Invalid opcode [%d] encountered at %d\n", opcode, c->program_counter - 1);
+    ic_instruction_halt(c);
+    break;
+  }
+}
+
+void ic_print(IC *c) {
+  printf("PC: %d\n", c->program_counter);
+  for (int i = 0; i < rom_count; i++) {
+    printf("%6d ", c->data[i]);
+    if (i % 8 == 7) printf("\n");
+  }
+  printf("\n");
+}
+
+void ic_reset(IC *c) {
+  memcpy(c->data, c->rom, rom_count * sizeof(int));
+  c->program_counter = 0;
+  c->halted = true;
+}
+
+void ic_run(IC *c) {
+  c->halted = false;
+  while (!c->halted) ic_execute_instruction(c);
+}
+
+IC *ic_new_computer(void) {
+  IC *c = malloc(sizeof(IC));
+  c->rom = rom;
+  c->data = malloc(rom_count * sizeof(int));
+  ic_reset(c);
+  return c;
+}
+
+int ic_load_rom_from_input(void) {
+  char *input = aoc_read_input();
+
+  char *token = strtok(input, ",");
+  while (token != NULL) {
+    rom[rom_count++] = atoi(token);
+    token = strtok(NULL, ",");
+  }
+
+  return rom_count;
+}