Darker and Darker

AtCoder

IDagc033_a

Time1000ms

Memory256MB

Difficulty—

You are given a grid of squares with $H$ horizontal rows and $W$ vertical columns, where each square is painted white or black. $HW$ characters from $A_{11}$ to $A_{HW}$ represent the colors of the squares. $A_{ij}$ is `#` if the square at the $i$\-th row from the top and the $j$\-th column from the left is black, and $A_{ij}$ is `.` if that square is white. We will repeatedly perform the following operation until all the squares are black: * Every white square that shares a side with a black square, becomes black. Find the number of operations that will be performed. The initial grid has at least one black square. ## Constraints * $1 \leq H,W \leq 1000$ * $A_{ij}$ is `#` or `.`. * The given grid has at least one black square. ## Input Input is given from Standard Input in the following format: $H$ $W$ $A_{11}$$A_{12}$$...$$A_{1W}$ $:$ $A_{H1}$$A_{H2}$$...$$A_{HW}$ [samples]

Samples

Input #1

3 3
...
.#.
...

Output #1

2

After one operation, all but the corners of the grid will be black. After one more operation, all the squares will be black.

Input #2

6 6
..#..#
......
#..#..
......
.#....
....#.

Output #2

API Response (JSON)

{
  "problem": {
    "name": "Darker and Darker",
    "description": {
      "content": "You are given a grid of squares with $H$ horizontal rows and $W$ vertical columns, where each square is painted white or black. $HW$ characters from $A_{11}$ to $A_{HW}$ represent the colors of the sq",
      "description_type": "Markdown"
    },
    "platform": "AtCoder",
    "limit": {
      "time_limit": 1000,
      "memory_limit": 262144
    },
    "difficulty": "None",
    "is_remote": true,
    "is_sync": true,
    "sync_url": null,
    "sign": "agc033_a"
  },
  "statements": [
    {
      "statement_type": "Markdown",
      "content": "You are given a grid of squares with $H$ horizontal rows and $W$ vertical columns, where each square is painted white or black. $HW$ characters from $A_{11}$ to $A_{HW}$ represent the colors of the sq...",
      "is_translate": false,
      "language": "English"
    }
  ]
}

Full JSON Raw Segments