CODEWITHSUNDEEP
c++arraysmultidimensional-arrayminesweeper
justin
justin

Reputation: 159

Checking adjacent indices in 2 dimensional array

I have to write minesweeper. I've figured out a way to check the adjacent indices to count how many bombs surround the current index without going out of bounds. But it's long, ugly, and most likely inefficient. They're just a bunch of conditional statements for each unique cell that could potentially reach out of bounds. My question is, is there a shorter way to do this? And would implementing a 1 dimensional warp-around array make it any easier/harder? 

int count = 0;
for (int i = 0; i < WIDTH; i++){
    for (int j = 0; j < HEIGHT; j++){
        **// index 0,0**
        if (i == 0 && j == 0 && field[i][j] != 10){
            if (field[i][j + 1] == 10)
                count++;
            if (field[i + 1][j] == 10)
                count++;
            if (field[i + 1][j + 1] == 10)
                count++;
        }
        **// index 0,9**
        else if (i == 0 && j == HEIGHT - 1 && field[i][j] != 10){
            if (field[i][j - 1] == 10)
                count++;
            if (field[i + 1][j - 1] == 10)
                count++;
            if (field[i + 1][j] == 10)
                count++;
        }

        **// index 9,0**
        else if (i == WIDTH - 1 && j == 0 && field[i][j] != 10){
            if (field[i - 1][j] == 10)
                count++;
            if (field[i][j + 1] == 10)
                count++;
            if (field[i - 1][j + 1] == 10)
                count++;
        }

        **// index 9,9**
        else if (i == WIDTH - 1 && j == HEIGHT - 1 && field[i][j] != 10){
            if (field[i - 1][j] == 10)
                count++;
            if (field[i][j - 1] == 10)
                count++;
            if (field[i - 1][j - 1] == 10)
                count++;
        }

        **// if first row**
        else if (i == 0 && (j != 0 && j != HEIGHT - 1) && field[i][j] != 10){
            if (field[i][j - 1] == 10)
                count++;
            if (field[i + 1][j - 1] == 10)
                count++;
            if (field[i + 1][j] == 10)
                count++;
            if (field[i + 1][j + 1] == 10)
                count++;
            if (field[i][j + 1] == 10)
                count++;
        }

        **// if last row**
        else if (i == WIDTH - 1 && (j != 0 && j != HEIGHT - 1) && field[i][j] != 10){
            if (field[i][j - 1] == 10)
                count++;
            if (field[i - 1][j - 1] == 10)
                count++;
            if (field[i - 1][j] == 10)
                count++;
            if (field[i - 1][j + 1] == 10)
                count++;
            if (field[i][j + 1] == 10)
                count++;
        }

        **// if first col**
        else if (j == 0 && (i != 0 && i != HEIGHT - 1) && field[i][j] != 10){
            if (field[i - 1][j] == 10)
                count++;
            if (field[i - 1][j + 1] == 10)
                count++;
            if (field[i][j + 1] == 10)
                count++;
            if (field[i + 1][j] == 10)
                count++;
            if (field[i + 1][j + 1] == 10)
                count++;
        }

        **// if last col**
        else if (j == HEIGHT - 1 && (i != 0 && i != WIDTH - 1) && field[i][j] != 10){
            if (field[i - 1][j - 1] == 10)
                count++;
            if (field[i - 1][j] == 10)
                count++;
            if (field[i][j - 1] == 10)
                count++;
            if (field[i + 1][j - 1] == 10)
                count++;
            if (field[i + 1][j] == 10)
                count++;
        }

        **// Cells that are fully surrounded**
        else if (field[i][j] != 10){
            if (field[i - 1][j - 1] == 10)
                count++;
            if (field[i - 1][j] == 10)
                count++;
            if (field[i - 1][j + 1] == 10)
                count++;
            if (field[i][j - 1] == 10)
                count++;
            if (field[i][j + 1] == 10)
                count++;
            if (field[i + 1][j - 1] == 10)
                count++;
            if (field[i + 1][j] == 10)
                count++;
            if (field[i + 1][j + 1] == 10)
                count++;
        }


        if (field[i][j] != 10)
            field[i][j] = count;
        count = 0;
    }
}

Upvotes: 0

Views: 3152

Answers (1)

Ivaylo Strandjev
Ivaylo Strandjev

Reputation: 70929

There is a standard way to deal with such situations - define an array with your valid moves and iterate over it. Here is an example how you can iterate over 8 neighboring cells:

static int moves[8][2] = {{-1,0}, {-1, -1}, {0, -1}, {1, -1}, {1, 0}, {1, 1}, {0, 1}, {-1, 1}};
for (int i = 0; i < WIDTH; i++) {
    for (int j = 0; j < HEIGHT; j++) {
      for (int l = 0; l < 8 /*sizeof(move) / sizeof(move[0]) */; ++l) {
        int ti = i + move[l][0];
        int tj = j + move[l][1];
        if (ti < 0 || ti >= WIDTH || tj < 0 || tj >= HEIGHT) {
          continue;
        }
        // cell (ti, tj) is valid neighbor do something with it.
      }
    }
}

Upvotes: 2

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