55 lines
1.9 KiB
Solidity
55 lines
1.9 KiB
Solidity
// SPDX-License-Identifier: MIT
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pragma solidity >=0.8.0 <0.9.0;
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library StatisticsUtils {
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/////////////////
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/// Errors //////
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/////////////////
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error EmptyArray();
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///////////////////
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/// Functions /////
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///////////////////
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/**
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* @notice Sorts an array of uint256 values in ascending order using selection sort
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* @dev Uses selection sort algorithm which is not gas-efficient but acceptable for small arrays.
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* This implementation mimics the early MakerDAO Medianizer exactly.
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* Modifies the input array in-place.
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* @param arr The array of uint256 values to sort in ascending order
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*/
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function sort(uint256[] memory arr) internal pure {
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uint256 n = arr.length;
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for (uint256 i = 0; i < n; i++) {
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uint256 minIndex = i;
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for (uint256 j = i + 1; j < n; j++) {
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if (arr[j] < arr[minIndex]) {
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minIndex = j;
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}
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}
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if (minIndex != i) {
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(arr[i], arr[minIndex]) = (arr[minIndex], arr[i]);
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}
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}
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}
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/**
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* @notice Calculates the median value from a sorted array of uint256 values
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* @dev For arrays with even length, returns the average of the two middle elements.
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* For arrays with odd length, returns the middle element.
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* Assumes the input array is already sorted in ascending order.
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* @param arr The sorted array of uint256 values to calculate median from
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* @return The median value as a uint256
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*/
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function getMedian(uint256[] memory arr) internal pure returns (uint256) {
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uint256 length = arr.length;
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if (length == 0) revert EmptyArray();
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if (length % 2 == 0) {
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return (arr[length / 2 - 1] + arr[length / 2]) / 2;
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} else {
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return arr[length / 2];
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}
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}
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}
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