Minimum Triggers to Clear All Balls

Question

Balls lie on a 2D plane, and balls[i] = [x_i, y_i] is the position of the i-th ball. A pair of balls is connected if it sits on one horizontal line (the y-coordinates match) or one vertical line (the x-coordinates match), with a gap of at most d between them on that line. For two balls on one row, the gap is |x_i - x_j|; on one column it is |y_i - y_j|. ...