import type { PositionStrategy } from './strategy';
/**
 * Position lookups for a uniform base size plus per-index overrides ("exceptions" — e.g. the
 * DOM-measured oversized rows on top of the default row height). Stores only the exceptions:
 * their sorted indexes and the prefix sums of their size deltas against the base. Building costs
 * O(exceptions log exceptions) — independent of the total item count — and every offset is
 * `index × base + binary-searched delta sum`. At 1M uniform rows with a few thousand oversized
 * rows this replaces a 1M-iteration prefix-sum build and an 8 MB allocation per rebuild.
 */
export declare class SparsePositionStrategy implements PositionStrategy {
    #private;
    /**
     * Sparse mode never holds a full prefix-sum array.
     *
     * @type {null}
     */
    readonly prefixSum: null;
    /**
     * @param {Record<number, number|undefined>} exceptions Per-index size overrides.
     * @param {number} totalItems The total item count read at build time.
     * @param {Function} sizeFn A function that returns the size for a given index.
     * @param {number} defaultSize The default item size read at build time.
     */
    constructor(exceptions: Record<number, number | undefined>, totalItems: number, sizeFn: (index: number) => number, defaultSize: number);
    /**
     * Returns the cumulative size before the given item index.
     *
     * @param {number} index The item index.
     * @returns {number} The cumulative size before this index.
     */
    getOffset(index: number): number;
    /**
     * Finds the item index at a given pixel offset by binary-searching the index space over
     * `getOffset` (O(log n log k)). Same return semantics as the prefix-sum strategy.
     *
     * @param {number} offset The pixel offset.
     * @returns {number} The index whose cumulative start position is at or just before the offset.
     */
    findIndexAtOffset(offset: number): number;
    /**
     * Returns the size of the single item at the given index.
     *
     * @param {number} index The item index.
     * @returns {number} The exception size, the base size, or `0` outside the item range.
     */
    getSizeAt(index: number): number;
    /**
     * Returns the total size of all items.
     *
     * @returns {number}
     */
    getTotalSize(): number;
}