Submission 3f696e92...

ChallengeRemove duplicate elements
Submitterhyszeth.eth
Submitted at2018-55-10
Gas used625542
/**
 * 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/
 */

pragma solidity 0.4.24;

contract Unique {
    event E(uint);
    /**
     * @dev Removes all but the first occurrence of each element from a list of
     *      integers, preserving the order of original elements, and returns the list.
     *
     * The input list may be of any length.
     *
     * @param input The list of integers to uniquify.
     * @return The input list, with any duplicate elements removed.
     */

    function uniquify(uint[] input) public pure returns(uint[] ret) {
        uint inputLength = input.length;
        if(inputLength == 0) return ret;

        uint inputLen = input.length;
        uint[] memory cache = new uint[](inputLen);

        uint uniqueIndex;

        uint nDups;
        for(uint i = 0; i < input.length; ++i) {
            	uint current = input[i];
		uint currentOffset = current + 0xfaccf431;
            	uint quickHash = 33 * current  % inputLen; // do we need a multiple? Like input * 33?
                uint elem;
		do {
			if(currentOffset == 0x0) {
				// Worst case
			}
			if((elem=cache[quickHash]) == currentOffset) {
				break; // duplicate
			} else if(elem == 0) {
				if(uniqueIndex != i) input[uniqueIndex] = current;
				uniqueIndex++;
				cache[quickHash] = currentOffset;
				break; // we have an original

			}
			quickHash = (quickHash+1)%inputLen;
		} while(true);
        }
        //emit E(r1);
        ret = new uint[](uniqueIndex);
        for(i = 0; i < uniqueIndex; ++i) {
            ret[i] = input[i];
        }
        return ret;
    }
}