Qt SCXML Sudoku Example

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 ** Copyright (C) 2016 The Qt Company Ltd.
 ** Contact: https://www.qt.io/licensing/
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 ** This file is part of the QtScxml module of the Qt Toolkit.
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 function restart() {
     for (var i = 0; i < initState.length; i++)
         currentState[i] = initState[i].slice();
     undoStack = [];
 }

 function isValidPosition() {
     var x = _event.data.x;
     var y = _event.data.y;
     if (x < 0 || x >= initState.length)
         return false;
     if (y < 0 || y >= initState.length)
         return false;
     if (initState[x][y] !== 0)
         return false;
     return true;
 }

 function calculateCurrentState() {
     if (isValidPosition() === false)
         return;
     var x = _event.data.x;
     var y = _event.data.y;
     var currentValue = currentState[x][y];
     if (currentValue === initState.length)
         currentValue = 0;
     else
         currentValue += 1;
     currentState[x][y] = currentValue;
     undoStack.push([x, y]);
 }

 function isOK(numbers) {
     var temp = [];
     for (var i = 0; i < numbers.length; i++) {
         var currentValue = numbers[i];
         if (currentValue === 0)
             return false;
         if (temp.indexOf(currentValue) >= 0)
             return false;
         temp.push(currentValue);
     }
     return true;
 }

 function isSolved() {
     for (var i = 0; i < currentState.length; i++) {
         if (!isOK(currentState[i]))
             return false;

         var column = [];
         var square = [];
         for (var j = 0; j < currentState[i].length; j++) {
             column.push(currentState[j][i]);
             square.push(currentState[Math.floor(i / 3) * 3 + Math.floor(j / 3)]
                                     [i % 3 * 3 + j % 3]);
         }

         if (!isOK(column))
             return false;
         if (!isOK(square))
             return false;
     }
     return true;
 }

 function undo() {
     if (!undoStack.length)
         return;

     var lastMove = undoStack.pop();
     var x = lastMove[0];
     var y = lastMove[1];
     var currentValue = currentState[x][y];
     if (currentValue === 0)
         currentValue = initState.length;
     else
         currentValue -= 1;
     currentState[x][y] = currentValue;
 }