Geometry

Combinatorial counting (pairs, ways to split), building the k-th permutation digit by digit, geometry (nearest point, law of cosines, triangle inequality), problems that become formulas after sorting or an observation, plus carry arithmetic, base conversion and fast exponentiation

LeetCode 3899 note: check the triangle inequality first, compute the three angles with the law of cosines, and remember to sort them

LeetCode 976 note: after sorting, check consecutive triples from the largest down; the first with a + b > c gives the largest perimeter

LeetCode 1401 note: the rectangle’s nearest point to the center is the center clamped into the rectangle; they overlap when that point is within the radius

Solving the Largest Rectangle in Histogram problem using monotonic stack approach

LeetCode 973 note: as in Top-K, keep a size-k max-heap (negated distances) holding the k closest points

LeetCode 1030 note: list every coordinate and sort by Manhattan distance to the center; return coordinates, not distances

LeetCode 892 note: a stack of v cubes has 4v + 2 faces; subtract 2 × min for each overlap with the stacks above and to the left

LeetCode 883 note: the top view counts nonzero cells, and the front and side views sum each row’s and each column’s maximum

LeetCode 836 note: two rectangles overlap exactly when their x intervals and y intervals both overlap, i.e. min(right) > max(left)

LeetCode 812 note: with at most 50 points, enumerate every triple and take the largest shoelace area