Created using remix-ide: Realtime Ethereum Contract Compiler and Runtime. Load this file by pasting this gists URL or ID at https://remix.ethereum.org/#version=soljson-v0.5.5+commit.47a71e8f.js&optimize=false&runs=200&gist=

contracts...NFTSimple.sol

pragma solidity >=0.4.24 <0.5.6;


contract NFTSimple { //Simple NFG

    string public name = "KlayLion";
    string public symbol = "KL"; // 단위

    //mint 발행 (tokenId, uri, owner) 
    //transform 전송 (from, to , uri)

    mapping (uint256 => address) public tokenOwner;
    mapping (uint256 => string) public tokenURIs; //map

    //배열 소유한 토큰 리스트 
    mapping(address => uint256[]) private _ownedTokens;

    function  mintWithTokenUri(address to, uint256 tokenId, string memory tokenURI) public returns (bool) {
        tokenOwner[tokenId] = to; //msg.sender 에게 토큰 id 발행
        tokenURIs[tokenId] = tokenURI; //글자  

        _ownedTokens[to].push(tokenId); //add Token to the list
        return true;
    } 

    function safeTransferform(address from, address to, uint256 tokenId) public {
        require(from == msg.sender, "from != msg.sender"); //조건
        require(from == tokenOwner[tokenId], "you are not the owner of the token");
        

        _removeTokenFromList(from, tokenId);
        _ownedTokens[to].push(tokenId);
        
        tokenOwner[tokenId] = to;


    }
    
    function _removeTokenFromList(address from, uint256 tokenId) private{
       
         //_ownedTokens[from] 
        //맨 뒤랑 바꾸고, 자르기
        uint256 lastTokenIdex = _ownedTokens[from].length-1;
        for (uint256 i = 0 ; i <= _ownedTokens[from].length; i ++){
            if (tokenId == _ownedTokens[from][i]) {
               // var temp = _ownedTokens[from][i]; //swap
                _ownedTokens[from][i] = _ownedTokens[from][lastTokenIdex];
                _ownedTokens[from][lastTokenIdex] = tokenId ;
                break;
            }
        }
        _ownedTokens[from].length--;
    }

    function ownedTokens(address owner) public view returns (uint256[] memory) {
        return _ownedTokens[owner];
    }


    function setTokenUri(uint256 id, string memory uri) public {
        tokenURIs[id] = uri;
    }
}


contract NFTMarket {
    
    
    function buyNFT(uint256 tokenId, address NFTAddress, address to ) public returns (bool) {
        NFTSimple(NFTAddress).safeTransferform(address(this), to, tokenId);
        return true;
    }
}