Submission e4f83ae0...

ChallengeInteger sorting
Submitterhyszeth.eth
Submitted at2018-45-23
Gas used776062
/**
 * This file is part of the 1st Solidity Gas Golfing Contest.
 *
 * This work is licensed under Creative Commons Attribution ShareAlike 3.0.
 * https://creativecommons.org/licenses/by-sa/3.0/
 *
 * Author: Greg Hysen (@hysz)
 * Date: June, 2018
 */

pragma solidity 0.4.24;

contract Sort {

    /**
     * @dev Sorts a list of integers in ascending order.
     *
     * The input list may be of any length.
     *
     * @param input The list of integers to sort.
     * @return The sorted list.
     */
     function sort(uint[] input)
      public
      pure
      returns(uint[])
    {
        if(input.length == 0) return input;
        quickSort(input, 0, input.length - 1);
        return input;
     }

        function quickSort(
            uint[] input,
            uint lo,
            uint hi
        )
         internal
         pure
        {
            uint iElem;
            uint jElem;
            if(hi - lo > 10) {
                // Pivot (Median of 3)
                i = uint((hi+lo)/2); // pivot index
                iElem = input[lo];
                uint pivot = input[i];
                jElem = input[hi];
                // [iElem, pivot, jElem]
                if(iElem > pivot) { // [pivot, iElem] [jElem]
                    if(iElem < jElem) {
                        // [pivot, iElem, jElem]
                        // Only swap pivot and iElem
                        (input[lo], input[i]) = (pivot, iElem);
                        pivot = iElem;
                    } else {
                        // [pivot, jElem, iElem] or [jElem, pivot, iElem]
                        if(jElem > pivot) {
                            // [pivot, jElem, iElem]
                            (input[lo], input[i], input[hi]) = (pivot, jElem, iElem);
                            pivot = jElem;
                        } else {
                            // [jElem, pivot, iElem]
                            (input[lo], input[hi]) = (jElem, iElem);
                        }
                    }
                } else {// if(iElem < pivot) { // [iElem, pivot] [jElem]
                    if(pivot > jElem) {
                        // [iElem, jElem, pivot] or [jElem, iElem, pivot]
                        if(jElem > iElem) {
                            // [iElem, jElem, pivot]
                            (input[i], input[hi]) = (jElem, pivot);
                            pivot = jElem;
                        } else {
                            // [jElem, iElem, pivot]
                            (input[lo], input[i], input[hi]) = (jElem, iElem, pivot);
                            pivot = iElem;
                        }
                    } else {
                        // [iElem, pivot, jElem]
                        // Do nothing
                    }
                }

                // Hoare pivot algorithm
                // Note we skip the lo/hi elements because
                // we already know they're in the correct position.
                uint i = lo;
                uint j = hi;
                while(true) {
                    while((iElem=input[uint(++i)]) <= pivot) {}
                    while((jElem=input[uint(--j)]) >= pivot) {}

                    if(i >= j) break;
                    input[uint(i)] = jElem;
                    input[uint(j)] = iElem;
                }

                // Sort
                quickSort(input, lo, j);
                quickSort(input, ++j, hi);
                return;
            }

            // If within threshold, run insertion sort instead.
            i = lo + 1;
            while(i <= hi) {
                jElem=input[(j = i)];
                while((iElem=input[j-1]) > jElem) {
                    input[j--] = iElem;
                    if(j == lo) break;
                }
                if(j != i++) input[j] = jElem;
            }
        }
}