My solution to a “Daily Coding Problem” that I received in my mail today.

Given a 2-D matrix representing an image, a location of a pixel in the screen and a color `C`, replace the color of the given pixel and all adjacent same colored pixels with `C`.

For example, given the following matrix, and location pixel of (2, 2), and ‘G’ for green:

``````B B W
W W W
W W W
B B B
``````

Becomes

``````B B G
G G G
G G G
B B B``````

Here’s my solution in Typescript. I actually like this problem a lot 🙂 Brings back memories of my computer vision research at the University of New South Wales.

``````oneFiftyOne(matrix: string[][], i:number, j: number, target: string): string[][] {
if(matrix == null) {
return [];
}
if(i < 0 || i >= matrix.length || j <0 || j>= matrix[i].length) {
return matrix;
}
if(matrix[i][j] == target) {
matrix[i][j] = "C";
} else {
return matrix;
}
this.oneFiftyOne(matrix, i+1, j, target);
this.oneFiftyOne(matrix, i-1, j, target);
this.oneFiftyOne(matrix, i, j+1, target);
this.oneFiftyOne(matrix, i, j-1, target);
return matrix;
}``````

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