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Commit17b0a94

Browse files
author
Raghav Dua
authored
Merge pull requestalgorithm-visualizer#201 from archie94/knight-tour
Implemented Knight's Tour:Backtracking method
2 parents979dc91 +9b458d8 commit17b0a94

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4 files changed

+102
-0
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4 files changed

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functionknightTour(x,y,moveNum){
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if(moveNum===N*N){
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returntrue;
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}
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for(vari=0;i<8;i++){
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varnextX=x+X[i];
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varnextY=y+Y[i];
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posTracer._notify(0,nextX)._wait();
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posTracer._notify(1,nextY)._wait();
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posTracer._denotify(0);
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posTracer._denotify(1);
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/*
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Check if knight is still in the board
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Check that knight does not visit an already visited square
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*/
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if(nextX>=0&&nextX<N&&nextY>=0&&nextY<N&&board[nextX][nextY]===-1){
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board[nextX][nextY]=moveNum;
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logTracer._print('Move to '+nextX+','+nextY);
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boardTracer._notify(nextX,nextY,moveNum)._wait();
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boardTracer._denotify(nextX,nextY);
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boardTracer._select(nextX,nextY);
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varnextMoveNum=moveNum+1;
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if(knightTour(nextX,nextY,nextMoveNum)===true){
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returntrue;
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}else{
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logTracer._print('No place to move from '+nextX+','+nextY+': Backtrack');
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board[nextX][nextY]=-1;// backtrack
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boardTracer._notify(nextX,nextY,-1)._wait();
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boardTracer._denotify(nextX,nextY);
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boardTracer._deselect(nextX,nextY);
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}
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}else{
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logTracer._print(nextX+','+nextY+' is not a valid move');
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}
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}
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returnfalse;
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}
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board[0][0]=0;// start from this position
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pos[0]=0;
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pos[0]=0;
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boardTracer._notify(0,0,0)._wait();
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posTracer._notify(0,0)._wait();
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posTracer._notify(1,0)._wait();
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boardTracer._denotify(0,0);
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boardTracer._denotify(0,0);
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posTracer._denotify(0);
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posTracer._denotify(1);
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if(knightTour(0,0,1)===false){
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logTracer._print('Solution does not exist');
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}else{
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logTracer._print('Solution found');
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}
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/*
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For N>3 the time taken by this algorithm is sufficiently high
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Also it is not possible to visualise for N>6 due to stack overflow
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caused by large number of recursive calls
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*/
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varN=3;
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varboard=newArray(N);
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for(vari=board.length-1;i>=0;i--){
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board[i]=newArray(N);
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}
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for(vari=board.length-1;i>=0;i--){
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for(varj=board[i].length-1;j>=0;j--){
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board[i][j]=-1;
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}
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}
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/*
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Define the next move of the knight
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*/
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varX=[2,1,-1,-2,-2,-1,1,2];
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varY=[1,2,2,1,-1,-2,-2,-1];
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varpos=newArray(2);
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pos[0]=pos[1]=-1;
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varboardTracer=newArray2DTracer('Board')._setData(board);
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varposTracer=newArray1DTracer('Knight Position')._setData(pos);
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varlogTracer=newLogTracer('Console');
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{
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"Knight’s tour problem":"A knight's tour is a sequence of moves of a knight on a chessboard such that the knight visits every square only once. If the knight ends on a square that is one knight's move from the beginning square (so that it could tour the board again immediately, following the same path), the tour is closed, otherwise it is open.",
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"Complexity": {
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"time":"Worst O(8<sup>N<sup>2</sup></sup>)",
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"space":"Worst O(N<sup>2</sup>)"
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},
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"References": [
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"<a href='https://en.wikipedia.org/wiki/Knight%27s_tour'>Wikipedia</a>"
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],
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"files": {
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"basic":"Solving the Knight’s tour problem using Backtracking & Recursion"
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}
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}

‎algorithm/category.json‎

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{
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"backtracking": {
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"list": {
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"knight's_tour":"Knight’s tour problem",
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"n_queens":"N Queens Problem"
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},
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"name":"Backtracking"

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