[FFC]no-repeats-please

有条件的全排列，允许重复，采用递归的方法

注意for循环的条件

function notRepeat(arr){
if(arr.length === 1){
  return true;
}
for(var i = 0 ; i < arr.length - 1; i++)
{
  if(arr[i] === arr[i+1])
    return false;
}
return true;
}
function swap(arr, i, j){
  var tmp = arr[i];
  arr[i] = arr[j];
  arr[j] = tmp;
  return arr;
}
function perm(arr,start, end){
   var count = 0;
   if(start === end){
    console.log(arr);
    if(notRepeat(arr)){
        return 1;
      }else{
        return 0;
      }
    } 
   for(var i = start ; i <= end ; i++){
      arr = swap(arr, start, i);
      count = count + perm(arr, start + 1, arr.length - 1);
      arr = swap(arr, start, i);
   }
    return count;
}



function permAlone(str){
    var arr = str.split("");
    var count = perm(arr, 0 , arr.length -1 );
    return count;

}
var a = permAlone("aab");
console.log(a);