d图像渐进填充

原文

import std;

struct point { int x, y; }

void show_grid(char[][] grid) {
  foreach (ref row ; grid)
    writeln(row);
  writeln;
}

void animated_fill(char[][] grid, point[] starting_points) {
  auto height = grid.length;
  if (height == 0)
    return;
  auto width = grid[0].length;

  struct xpoint { int x, y, dist_from_start; }
  auto queue = uninitializedArray!(xpoint[])(width * height);
  size_t start, end;

  foreach (p ; starting_points) {
    if (grid[p.y][p.x] == '.') {
      queue[end++] = xpoint(p.x, p.y, 0);
      grid[p.y][p.x] = '#';
    }
  }

  int current_dist = -1;
  while (start < end) {
      auto p = queue[start++];

      if (p.dist_from_start > current_dist) {
        show_grid(grid);
        current_dist = p.dist_from_start;
      }

      if (p.y + 1 < height && grid[p.y + 1][p.x] == '.') {
        queue[end++] = xpoint(p.x, p.y + 1, p.dist_from_start + 1);
        grid[p.y + 1][p.x] = '#';
      }
      if (p.y - 1 >= 0 && grid[p.y - 1][p.x] == '.') {
        queue[end++] = xpoint(p.x, p.y - 1, p.dist_from_start + 1);
        grid[p.y - 1][p.x] = '#';
      }
      if (p.x + 1 < width && grid[p.y][p.x + 1] == '.') {
        queue[end++] = xpoint(p.x + 1, p.y, p.dist_from_start + 1);
        grid[p.y][p.x + 1] = '#';
      }
      if (p.x - 1 >= 0 && grid[p.y][p.x - 1] == '.') {
        queue[end++] = xpoint(p.x - 1, p.y, p.dist_from_start + 1);
        grid[p.y][p.x - 1] = '#';
      }
  }
}

void main() {
  auto grid = ["....@.....".dup,
               "....@@@@..".dup,
               "..........".dup];
  auto height = grid.length.to!int;
  auto width = grid[0].length.to!int;

  const number_of_starting_points = 2;
  auto random_points = new point[](number_of_starting_points);
  foreach (ref p ; random_points)
    p = point(uniform(0, width), uniform(0, height));

  animated_fill(grid, random_points);
}