Area of Overlapping Rectangles — Solution & Editorial

Back to the Problem

Coordinate-compress the x-boundaries into slabs; for each slab, the covered height is the union of the y-intervals of rectangles spanning it. Sum width×covered-height. (A segment tree over y scales to N = 10⁵.)

Complexity: O(N²)

Watch out: Areas reach ~4×10⁸; and the y-interval union per slab must merge overlaps.