Exactly K Flights — Solution & Editorial

Back to the Problem

Min-plus (tropical) matrix power: replace (+, ×) with (min, +); A^K under this semiring gives cheapest exactly-K-edge walks. Same binary exponentiation skeleton.

Complexity: O(N³ log K)

Watch out: The identity element is the INF-off-diagonal matrix (0 on the diagonal), not the all-zero matrix.