/**
 * Longest Increasing Subsequence — O(n log n).
 *
 * Given an array of numbers, returns the Set of *indices* into that array
 * whose elements form the longest strictly increasing subsequence.
 * Entries equal to -1 are skipped (treated as "not present").
 *
 * Used by the keyed reconciler to identify the maximal set of children
 * that are already in correct relative order and don't need DOM moves.
 */
export declare function lis(arr: number[]): Set<number>;