比特币上的数独游戏合约的实现代码

我们在 bitcoin sv 上实现了一个数独游戏智能合约，利用之前介绍过的一种可以将游戏中寻找解题方案的过程外包上链。因为求解数独问题的计算工作量会随着其行列数快速增长，实际上它也是一个 np-完全 问题。不过我们可以借由比特币智能合约巧妙地寻求答案，只需要验证答案提供者所给出的解答是否满足要求即可，这样即可以将复杂的求解计算过程实现链下外包。

scrypt 合约代码如下：

import "util.scrypt";
import "array.scrypt";

contract sudoku {

 bytes board;

 static const int n = 9;
 static bytes empty = b'00';

 constructor(bytes board) {
  this.board = board;
 }

 function merge(bytes solution) : bytes {
  bytes newboard = this.board;
  int i = 0;
  loop (n) {
   int j = 0;
   loop (n) {

    int value = this.readvalue(newboard, i, j);
    int inputvalue = this.readvalue(solution, i, j);
    if (value == 0) {
     require(inputvalue <= 9);
     newboard = this.setvalue(newboard, i, j, inputvalue);
    } else {
     require(value == inputvalue);
    }
    j++;
   }

   i++;
  }
  return newboard;
 }

 public function solve(bytes solution) {

  require(len(solution) == sudoku.n * sudoku.n);

  bytes newbord = this.merge(solution);

  array rowarray = new array();
  array colarray = new array();
  array squarearray = new array();

  int i = 0;
  loop (n) {
   int j = 0;

   loop (n) {
    // check for duplicate

    // in a row
    int rowelem = this.readvalue(newbord, i, j);
    require(rowarray.indexof(rowelem) == -1);
    rowarray.push(rowelem);

    // in a column
    int colelem = this.readvalue(newbord, j, i);
    require(colarray.indexof(colelem) == -1);
    colarray.push(colelem);

    // in a subgrid
    int squareelem = this.readsquarevalue(newbord, i, j);
    require(squarearray.indexof(squareelem) == -1);
    squarearray.push(squareelem);

    j++;
   }

   rowarray.clear();
   colarray.clear();
   squarearray.clear();

   i++;
  }

  require(true);
 }

 static function readvalue(bytes board, int i, int j): int {
  return util.fromleunsigned(util.getelemat(board, sudoku.index(i, j)));
 }

 static function setvalue(bytes board, int i, int j, int value): bytes {
  return util.setelemat(board, this.index(i, j), util.toleunsigned(value, 1));
 }

 static function readsquarevalue(bytes board, int i, int j): int {
  return util.fromleunsigned(util.getelemat(board, sudoku.indexsquare(i, j)));
 }


 static function index(int row, int col) : int {
  return row * sudoku.n + col;
 }

 static function indexsquare(int i, int j) : int {
  int row = i / 3 * 3 + j / 3;
  int col = i % 3 * 3 + j % 3;
  return sudoku.index(row, col);
 }
}

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