Question

Given a set of points on a plane, find the shortest line segment formed by any two of these points.

How can I do that? The trivial way is obviously to calculate each distance, but I need another algorithm to compare.

Answer 1

http://en.wikipedia.org/wiki/Closest_pair_of_points

The problem can be solved in O(n log n) time using the recursive divide and conquer approach, e.g., as follows:

• Sort points along the x-coordinate
• Split the set of points into two equal-sized subsets by a vertical line x = xmid
• Solve the problem recursively in the left and right subsets. This will give the left-side and right-side minimal distances dLmin and dRmin respectively.
• Find the minimal distance dLRmin among the pair of points in which one point lies on the left of the dividing vertical and the second point lies to the right.
• The final answer is the minimum among dLmin, dRmin, and dLRmin.