查找数组中的交集元素

Question

我需要构造一个函数交集，它比较输入数组并返回一个新的数组，其中包含在所有输入中找到的元素。如果每个数组中的数字只重复一次，则以下解决方案有效，否则将中断。另外，我不知道如何简化并且不使用杂乱的for循环：

function intersection(arrayOfArrays) {
  let joinedArray = [];
  let reducedArray = [];
  for (let iOuter in arrayOfArrays) {
    for (let iInner in arrayOfArrays[iOuter]) {
      joinedArray.push(arrayOfArrays[iOuter][iInner]);
    }
    return joinedArray;
  }


  for (let i in joinedArray.sort()) {
    if (joinedArray[i] === joinedArray[ i - (arrayOfArrays.length - 1)]) {
      reducedArray.push(joinedArray[i]);
    }
  }
  return reducedArray;
}

Answer 1

试试这个：-

function a1(ar,ar1){
    x = new Set(ar)
    y = new Set(ar1)
    var result = [] 
    for (let i of x){
        if (y.has(i)){
            result.push(i)
        }
    }
    if (result){return result}
    else{ return 0}
}
var a= [3,4,5,6]
var b = [8,5,6,1]
console.log(a1(a,b)) //output=> [5,6]

Answer 2

希望这段代码对我们有用。

​

var a = [2, 3, 9];
var b = [2, 8, 9, 4, 1];
var c = [3, 4, 5, 1, 2, 1, 9];
var d = [1, 2]

function intersect() {
  // create an empty array to store any input array,All the comparasion
  // will be done against this one
  var initialArray = [];
  // Convert all the arguments object to array
  // there can be n number of supplied input array
  // sorting the array by it's length. the shortest array 
  //will have at least all the elements
  var x = Array.prototype.slice.call(arguments).sort(function(a, b) {
    return a.length - b.length
  });
  initialArray = x[0];
  // loop over remaining array
  for (var i = 1; i < x.length; i++) {
    var tempArray = x[i];
    // now check if every element of the initial array is present
    // in rest of the arrays
    initialArray.forEach(function(item, index) {
      // if there is some element which is present in intial arrat but not in current array
      // remove that eleemnt.
      //because intersection requires element to present in all arrays
      if (x[i].indexOf(item) === -1) {
        initialArray.splice(index, 1)
      }

    })

  }
  return initialArray;
}

console.log(intersect(a, b, c, d))

​

Answer 3

有一种很好的方法，使用reduce来遍历数组数组，然后使用filter来使剩余的值唯一。

function intersection(arrayOfArrays) {
    return arrayOfArrays
        .reduce((acc,array,index) => { // Intersect arrays
            if (index === 0)
                return array;
            return array.filter((value) => acc.includes(value));
        }, [])
        .filter((value, index, self) => self.indexOf(value) === index) // Make values unique
    ;
}