Lundi 7

#include <stdio.h>
#include <stdlib.h>
#include <memory.h>

#undef uint
#define uint unsigned int

static inline void zero_buf(uint **buf, uint w, uint h) {
 for(uint i=0; i<h; i++)
  memset(buf[i], '\0', w * sizeof(**buf));
}

static inline void free_buf(void *_buf, uint h) {
 char **buf = (char **)_buf;
 if(!buf) return;
 for(uint i=0; i<h; i++)
  free(buf[i]);
 free(buf);
}

static inline void *alloc_zero_buf(uint w, uint h, uint elem_len) {
 char **buf;

 buf = malloc(h * sizeof(void *));
 if(!buf) return NULL;

 for(uint i=0; i<h; i++) {
  buf[i] = malloc(w * elem_len);
  if(!buf[i]) goto fail_free;
  memset(buf[i], '\0', w * elem_len);
 }
 return buf;

fail_free:
 for(uint i=0; buf[i] && i<h; i++)
  free(buf[i]);
 free(buf);
 return NULL;
}

static inline char **read_input_buf(uint w, uint h) {
 char **buf;

 buf = alloc_zero_buf(w+2, h, sizeof(**buf)); /* w+2 for "\n\0" */
 if(!buf) {
  fprintf(stderr, "E: Alloc input buffer.\n");
  return NULL;
 }

 for(uint i=0; i<h; i++) {
  if(feof(stdin) || ferror(stdin)) {
   fprintf(stderr, "E: Incomplete buffer.\n");
   goto fail_free;
  }
  fgets(buf[i], w+2, stdin);
  if(strlen(buf[i]) != w+1) {
   fprintf(stderr, "E: Incomplete buffer line.\n");
   goto fail_free;
  }
 }
 return buf;

fail_free:
 free_buf(buf, h);
 return NULL;
}

static inline uint draw(char **data_buf, uint **draw_buf, uint **depth_buf, uint y, uint x, uint w, uint h) {
 uint count = 1;

 if(depth_buf[y][x]) return 0;
 zero_buf(draw_buf, w, h);

 while(!depth_buf[y][x]) {
  depth_buf[y][x] = 1;
  draw_buf[y][x] = count++;

  switch(data_buf[y][x]) {
   case '<': x = (!x) ? w-1 : x-1; break;
   case '^': y = (!y) ? h-1 : y-1; break;
   case '>': x = (x == w-1) ? 0 : x+1; break;
   case 'v': y = (y == h-1) ? 0 : y+1; break;
   default:
    depth_buf[y][x] = 0;
    fprintf(stderr, "E: Invalid character at (%u,%u): '%c'.\n", x, y, data_buf[y][x]);
    return -1;
  }
 }
 if(!draw_buf[y][x]) return 0;
 return count-draw_buf[y][x];
}

int main(int argc, char **argv)
{
 int res = -1;
 uint w = 0, h = 0;
 uint max_len = 0;
 char **data_buf = NULL;
 uint **draw_buf = NULL;
 uint **depth_buf = NULL;

 if(fscanf(stdin, "%u %u", &w, &h) != 2 || !w || !h) {
  fprintf(stderr, "E: Invalid size specified.\n");
  return -1;
 }
 fgetc(stdin); /* Trailing \n */

 data_buf = read_input_buf(w, h);
 if(!data_buf) {
  fprintf(stderr, "E: Read input buffer.\n");
  goto free_exit;
 }

 draw_buf = alloc_zero_buf(w, h, sizeof(**draw_buf));
 if(!draw_buf) {
  fprintf(stderr, "E: Alloc draw buffer.\n");
  goto free_exit;
 }

 depth_buf = alloc_zero_buf(w, h, sizeof(**depth_buf));
 if(!depth_buf) {
  fprintf(stderr, "E: Alloc depth buffer.\n");
  goto free_exit;
 }

 for(uint i=0; i<h; i++) {
  for(uint j=0; j<w; j++) {
   uint new_len = 0;
   new_len = draw(data_buf, draw_buf, depth_buf, i, j, w, h);
   if(new_len < 0)
    goto free_exit;
   if(new_len > max_len)
    max_len = new_len;
  }
 }
 fprintf(stdout, "Max loop: %u.\n", max_len);

 res = 0;

free_exit:
 free_buf(data_buf, h);
 free_buf(draw_buf, h);
 free_buf(depth_buf, h);
 return res;
}