阵列之间的对称差异 [英] symmetric difference between arrays

问题描述

我一直在编写代码，以使to或多个数组之间产生对称差异.如您所知，对称差异就是要排除两组数据中的元素.更多信息: https://en.wikipedia.org/wiki/Symmetric_difference

I have been writing the code to make a symmetric difference between to or more arrays. As you know, the symmetric difference is about excluding the elements which are in both sets of datas. More info: https://en.wikipedia.org/wiki/Symmetric_difference

这是我的代码:

  //This function drops any repeated element from a vector
    function unify(arr){
        var result=arr.reduce(function(vector,num,index,self){
         var len=self.filter(function (val){
           return val===num;
         }).length;
        if (len>1){
          var pos=self.indexOf(num);
          self.splice(pos,1);
        }
        vector=self;
        return vector;
        },[]);
      
      return result;
    }
    
    function sym(args) {
      var arg = Array.prototype.slice.call(arguments); 
      var compact= arg.map(function(vector){
        return unify(vector);
      });
      
      //We compare the vectors and delete any repeated element before we concat them
      return compact.reduce(function(prev,next,index,self){
        for (var key in next) {
          var entry=next[key];
          var pos=prev.indexOf(entry);
          if (pos!==-1){
            prev.splice(pos,1);
            next.splice(key,1);
          }
            
        }
        return prev.concat(next);
      });
      
    }
    
    console.log(sym([1, 2, 3], [5, 2, 1, 4]));

我不明白我在做什么错.我期望得到[3,4,5]的结果，但这不是我得到的结果.

I don't understand what am I doing wrong. I expected to get a result of [3,4,5] but that is not the result I get.

推荐答案

进行拼接时，将更改数组的索引.因此它将跳过一些值.

When you do the splice, the indexing of the array is changed. So it would skip some values.

在您的示例中，为prev = [1,2,3]和next = [5,2,1,4].

In your example, prev = [1,2,3] and next = [5,2,1,4].

在第一个接头@ key = 1之后，两个数组都看起来像这样prev = [1,3]和next = [5,1,4].下一个键是2，它会跳过next中的条目1.由于存在接头，因此该索引向左移动了一个.

After the first splice @ key = 1 both arrays look like this prev = [1,3] and next = [5,1,4]. The next key is 2 which skips the entry 1 in next. Because of the splice, this index has shifted one to the left.

我的解决方案(对不起，我在手机上，否则我会写代码)

My solutions (sorry, I'm on my phone else I'd have written code)

1. 编写一个更深思熟虑的循环，并仅在必要时增加键. 因此，如果有接头，请不要增加，因为下一个可能 条目已移至当前键.
2. 如果必须保持for a in b型循环，请考虑重复但恒定 next数组的参考

1. Write a more deliberate loop, and increment key only when necessary. So if there's a splice, don't increment, because the would-be next entry has been shifted to the current key.
2. If you must keep the for a in b-type loop, consider having a duplicate but constant reference for the next array

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