adventofcode/2015/day03/day03.c

#include <stdio.h>

void part1() {
  printf("Part 1\n");

  char ch = getchar();
  int visits[1000][1000];
  for(int i = 0; i < 1000; i++) {
    for(int j = 0; j < 1000; j++) {
      visits[i][j] = 0;
    }
  }
  int x = 0, y = 0, minx = 0, maxx = 0, miny = 0, maxy = 0;
  int inc = 0;
  while(ch) {
    visits[x+500][y+500]++;
    if(ch == '\n') { break; }
    switch(ch) {
    case '>':
      x++;
      break;
    case 'v':
      y--;
      break;
    case '<':
      x--;
      break;
    case '^':
      y++;
      break;
    }
    if(x > maxx) {
      maxx = x;
    }
    if(x < minx) {
      minx = x;
    }
    if(y > maxy) {
      maxy = y;
    }
    if(y < miny) {
      miny = y;
    }
    ch = getchar();
  }
  int result = 0;
  for(int i = 0; i < 1000; i++) {
    for(int j = 0; j < 1000; j++) {
      if(visits[i][j] > 0) {
        result++;
      }
    }
  }
  printf("%d houses\n", result);
}

void part2() {
  printf("Part 2\n");
  char ch = getchar();
  int visits[1000][1000];
  for(int i = 0; i < 1000; i++) {
    for(int j = 0; j < 1000; j++) {
      visits[i][j] = 0;
    }
  }
  int x1 = 0, y1 = 0, x2 = 0, y2 = 0, minx = 0, maxx = 0, miny = 0, maxy = 0;
  int inc = 0;
  int robo = -1;
  int lastOutLngth = 0;
  while(ch) {
    robo++;
    int usex = x1, usey = y1;
    if(robo % 2 == 1) {
      usex = x2;
      usey = y2;
    }
    visits[usex+500][usey+500]++;
    if(ch == '\n') { break; }

    switch(ch) {
    case '>':
      usex++;
      break;
    case 'v':
      usey--;
      break;
    case '<':
      usex--;
      break;
    case '^':
      usey++;
      break;
    }

    if(usex > maxx) {
      maxx = usex;
    }
    if(usex < minx) {
      minx = usex;
    }
    if(usey > maxy) {
      maxy = usey;
    }
    if(usey < miny) {
      miny = usey;
    }
    // Get the next char
    if(robo % 2 == 1) {
      x2 = usex;
      y2 = usey;
    } else {
      x1 = usex;
      y1 = usey;
    }
    ch = getchar();
  }

  // Now find how many houses got presents
  int result = 0;
  for(int i = 0; i < 1000; i++) {
    for(int j = 0; j < 1000; j++) {
      if(visits[i][j] > 0) {
        result++;
      }
    }
  }

  printf("%d houses\n", result);
}

int main(int argc, char **argv) {
  int doPart = 1;
  if(argc > 1) { doPart = argv[1][0] - '0'; }
  if(doPart == 1) {
    part1();
  } else {
    part2();
  }
  return 0;
}