问二维网格上最大可达面积的动态规划问题

EN

bool isSafe(int x, int y){
    return (sum(Math.Abs(x)) + sum(Math.Abs(y))) < 24;
}

int sum(int n){
    int ret = 0;        
    while(n > 0){
        ret += n%10;
        n = n/10;
    }
    return ret;
}

var visited = new bool[2000, 2000];
var queue = new Queue<(int x, int y)>();

var steps = new List<(int di, int dj)>() {(-1, 0), (1, 0), (0, -1), (0, 1)};

int count = 1; 

queue.Enqueue((0, 0));
visited[1000, 1000] = true;

while (queue.Count != 0)
{
    var point = queue.Dequeue();
    foreach (var step in steps)
        if (!visited[point.x + step.di + 1000, point.y + step.dj + 1000] && isSafe(point.x + step.di, point.y + step.dj))
        {
            count++;
            visited[point.x + step.di + 1000, point.y + step.dj + 1000] = true;
            queue.Enqueue((point.x + step.di, point.y + step.dj));
        }
}

Console.WriteLine(count);   

592597

#include <cmath>
#include <iostream>

const int SQUARE_SIDE = 1'000;

// v[i][j] is true if cell (i - SQUARE-SIDE, j - SQUARE_SIDE) was already
// visited during DFS, false otherwise.
bool v[2 * SQUARE_SIDE][2 * SQUARE_SIDE];
int answer = 0;

const struct {
  int dx;
  int dy;
} moves[] = {
    {1, 0},   // Up
    {-1, 0},  // Down
    {0, -1},  // Left
    {0, 1}    // Right
};

int calc_abs_sum(int n) {
  n = abs(n);
  int sum = 0;
  while (n) {
    sum += n % 10;
    n /= 10;
  }
  return sum;
}

void dfs(int x, int y) {
  // Add SQUARE_SIDE to make indices non-negative.
  v[x + SQUARE_SIDE][y + SQUARE_SIDE] = true;
  answer++;

  for (const auto &move : moves)
    if (calc_abs_sum(x + move.dx) + calc_abs_sum(y + move.dy) <= 23 &&
        !v[x + move.dx + SQUARE_SIDE][y + move.dy + SQUARE_SIDE]) {
      dfs(x + move.dx, y + move.dy);
    }
}

int main() {
  dfs(0, 0);
  std::cout << answer << std::endl;
}