请教一下大佬们二维矩阵的 DFS 问题，不知道为什么总是报错

业务场景：

有个二维矩阵 513 * 513 ，取值只有 0 或 1 ，根据值绘图，0 白色 1 黑色。 现在需要把不规则的黑色绘制成矩形，如下图：

代码如下：

func findConnectedRegion(matrix: [[Int]]) -> [[(Int, Int)]] { var result: [[(Int, Int)]] = [] // var visited: Set<(Int, Int)> = [] var visited: Set<String> = [] let numRows = matrix.count let numCols = matrix[0].count for i in 0..<matrix.count { for j in 0..<matrix[0].count { let position = (i, j) let str = String(i)+"-"+String(j) if matrix[i][j] == 1 && !visited.contains(str) { var region: [(Int, Int)] = [] dfs(matrix: matrix, rows: numRows,cols: numCols,position: position, visited: visited, region: &region) result.append(region) } } } return result } func dfs(matrix: [[Int]],rows:Int,cols:Int,position: (Int, Int), visited: Set<String>, region: inout [(Int, Int)]) { // let numRows = matrix.count // let numCols = matrix[0].count let numRows = rows let numCols = cols let (row, col) = position self.str = String(position.0)+"-"+String(position.1) // Check if the current position is within bounds and is part of the region guard row >= 0, row < numRows, col >= 0, col < numCols, matrix[row][col] == 1, !visited.contains(str) else { return } self.visited.insert(str) region.append(position) // Explore neighbors in all four directions dfs(matrix: matrix,rows: numRows,cols: numCols, position: (row - 1, col), visited: visited, region: &region) // Up dfs(matrix: matrix, rows: numRows,cols: numCols,position: (row + 1, col), visited: visited, region: &region) // Down dfs(matrix: matrix, rows: numRows,cols: numCols,position: (row, col - 1), visited: visited, region: &region) // Left dfs(matrix: matrix, rows: numRows,cols: numCols,position: (row, col + 1), visited: visited, region: &region) // Right } 

好几处局部变量改成了属性，但还是不同位置报相同的错：Thread 1: EXC_BAD_ACCESS (code=2, address=0x16b6a7fc0)

完全不知道问题出在哪了，请大佬指点