Javascript Maze Runner 出现 Codewars 错误

Question

我一直在研究代码 war ，并且遇到了 mazerunner (https://www.codewars.com/kata/maze-runner/train/javascript)，我已经被难住了大约 2 天!

function mazeRunner(maze, directions) {

//find start value  

var x = 0; //x position of the start point
var y = 0; //y position of the start point

for (var j = 0 ; j < maze.length ; j++){
if (maze[j].indexOf(2) != -1){
  x = j;
  y = maze[j].indexOf(2)
}
      } // end of starting position forloop

console.log(x + ', ' + y)


  for (var turn = 0 ; turn < directions.length ; turn++){


if (directions[turn] == "N"){
 x -= 1;
}
if (directions[turn] == "S"){
 x += 1;
}
if (directions[turn] == "E"){
 y += 1;
}
if (directions[turn] == "W"){
 y -= 1;
}

 if (maze[x][y] === 1){
 return 'Dead';
 }else if (maze[x][y] === 3){
 return 'Finish';
 }

if (maze[x] === undefined || maze[y] === undefined){
return 'Dead';
}

}

return 'Lost';

}

当我运行它时，它适用于大多数情况，但是在最后一个情况下我收到以下错误

TypeError: Cannot read property '3' of undefined
at mazeRunner
at /home/codewarrior/index.js:87:19
at /home/codewarrior/index.js:155:5
at Object.handleError

如有任何帮助，我们将不胜感激!我正为这个而揪心呢!

Answer 1

你的解决方案的问题是，移动后，你只需检查maze[x][y]的值

在失败的测试中，maze[x] 将在某个时刻未定义(向南移动一段时间)。我猜想在同一点 y 将是 3，因此错误 Cannot read property '3' of undefined

为了避免这种情况，您应该在尝试访问坐标之前将测试未定义的代码上移:

// move this as first check
if (maze[x] === undefined || maze[y] === undefined){
  return 'Dead';
}