Multidimensional array fill

Question

I\'m trying to fill an area in a multidimensional array and not sure on the approach.

For example I have the following array:

var map = [
    [0, 0,          


        

Answer 1

Assuming you're given a starting position and you want to then fill all neighboring values up/down, left/right that contain the same value, you can do something like this:

var map = [
    [0, 0, 0, 0, 0, 0, 0, 0, 0],
    [0, 2, 2, 2, 2, 2, 2, 0, 0],
    [0, 2, 0, 0, 0, 0, 2, 0, 0],
    [0, 2, 0, 2, 0, 0, 2, 0, 0],
    [0, 2, 0, 0, 2, 0, 2, 0, 0],
    [0, 0, 2, 0, 0, 0, 2, 0, 0],
    [0, 0, 0, 2, 2, 2, 2, 0, 0],
    [0, 0, 0, 0, 0, 0, 0, 0, 0]
];

function fill(data, x, y, newValue) {
    // get target value
    var target = data[x][y];

    function flow(x,y) {
        // bounds check what we were passed
        if (x >= 0 && x < data.length && y >= 0 && y < data[x].length) {
            if (data[x][y] === target) {
                data[x][y] = newValue;
                flow(x-1, y);    // check up
                flow(x+1, y);    // check down
                flow(x, y-1);    // check left
                flow(x, y+1);    // check right
            }
        }
    }

    flow(x,y);
}

fill(map, 2, 2, 1);

Working demo: http://jsfiddle.net/jfriend00/C83AT/

---

Here's a version that doesn't use recursion and appears to work with large data sets. Your large test data set wasn't a very interesting test pattern so I wouldn't say this is tested conclusively, but it seems to work on both the small and large data set:

Large data example: http://jsfiddle.net/jfriend00/8mrhN/

Small data example: http://jsfiddle.net/jfriend00/BFTub/ (easier to see the result)

function fill(data, x, y, newValue) {
    // get target value
    var target = data[x][y];
    // maintain list of cells to process
    // put the starting cell in the queue
    var queue = [{x:x, y:y}], item;

    while (queue.length) {
        item = queue.shift();
        x = item.x;
        y = item.y;
        if (data[x][y] === target) {
            data[x][y] = newValue;
            // up
            if (x > 0) {
                queue.push({x:x-1, y:y})
            }
            // down
            if (x + 1 < data.length) {
                queue.push({x:x+1, y:y})
            }
            // left
            if (y > 0) {
                queue.push({x:x, y:y-1});
            }
            // right
            if (y + 1 < data[x].length) {
                queue.push({x:x, y:y+1});
            }
        }
    }
}

This could be optimized further for performance by testing the value before putting it in the queue and by following a given direction until you find a non-matching value, if required.