Javascript数组末尾追加0

Question

我正在解决这个问题

Given an array of numbers, I need to move all zeros at the end of thearray (in-place without making a copy of an array)

For example: given nums = [0, 1, 0, 3, 12]

After calling yourfunction, nums should be [1, 3, 12, 0, 0].

我的尝试:

   var moveZeroes = function(nums) {
      var count=0;
      
      //Remove anything that's not Zero.
      nums.forEach(function(val, index){
        if(val==0){
          nums.splice(index, 1);
          count++;
        }
      });
    
      //Fill in Zeros at the end
      for(var i=0; i< count ; i++){
        nums.push(0);
      }
    };
    
    
    var input1 = [0,1,0,3,12];
    var input2 = [0,0,1];
    
    moveZeroes(input1)
    console.log(input1); //Works!
    
    moveZeroes(input2)
    console.log(input2); //fails!

问题:

它适用于诸如 [0,1,0,3,12] 之类的输入，但在诸如 [0,0,1] 之类的输入中失败(输出我得到的是 0,1,0);为什么？我该如何修复它？

Answer 1

您从当前正在循环的数组中剪切(拼接)(在forEach中)，因此有更多连续的0 其中一些将被跳过。

因此，如果数组是[0, 0, 1]，则会发生以下情况:

forEach: (case of two or more successive 0s)

    [0, 0, 1]
//   ^ cursor is here (0 === 0 then remove it)
    [0, 1]
//      ^ cursor is at the second item, the second 0 is safe because it is now occupy a place that is already looped over
    [0, 1]
// fails

forEach: (case of no successive 0s)

    [0, 1, 0, 1]
//   ^ cursor is here (0 === 0 then remove it)
    [1, 0, 1]
//      ^ (0 === 0 then remove) 
    [1, 1]
// works

要解决这个问题，您必须使用基本的 for 循环，您可以在其中控制光标(索引)的位置，或者以不改变其长度的方式更改数组并且不将 0 隐藏在光标后面，如下所示:

var moveZeroes = function(nums) {
  nums.forEach(function(val, index) {
    if (val) {               // if it is a non-zero value
      nums.splice(index, 1); // remove it
      nums.unshift(val);     // add it to the begining of the array (note that the order of non-zero values will be reversed)
    }
  });
};


var input1 = [0, 1, 0, 3, 12];
var input2 = [0, 0, 1];

moveZeroes(input1)
console.log(input1); //Works!

moveZeroes(input2)
console.log(input2); // Now Works too!