48 lines
1.4 KiB
Solidity
48 lines
1.4 KiB
Solidity
// SPDX-License-Identifier: MIT
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pragma solidity ^0.6.0;
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import "../math/Math.sol";
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/**
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* @dev Collection of functions related to array types.
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*/
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library Arrays {
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/**
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* @dev Searches a sorted `array` and returns the first index that contains
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* a value greater or equal to `element`. If no such index exists (i.e. all
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* values in the array are strictly less than `element`), the array length is
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* returned. Time complexity O(log n).
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*
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* `array` is expected to be sorted in ascending order, and to contain no
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* repeated elements.
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*/
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function findUpperBound(uint256[] storage array, uint256 element) internal view returns (uint256) {
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if (array.length == 0) {
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return 0;
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}
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uint256 low = 0;
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uint256 high = array.length;
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while (low < high) {
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uint256 mid = Math.average(low, high);
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// Note that mid will always be strictly less than high (i.e. it will be a valid array index)
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// because Math.average rounds down (it does integer division with truncation).
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if (array[mid] > element) {
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high = mid;
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} else {
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low = mid + 1;
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}
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}
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// At this point `low` is the exclusive upper bound. We will return the inclusive upper bound.
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if (low > 0 && array[low - 1] == element) {
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return low - 1;
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} else {
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return low;
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}
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}
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}
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