JavaScript：如何使数组中的两个元素等于任何给定数字

Question

My question is:

If I have a array like this, example:

var myArray = [1,2,4,6,9]

and I want to get the number 15 by getting (adding) the index of 6 and 9.

How do I do that?

I can't make it work and I have tried endlessly... please help.

My attempt:

var list = [1,3,5,7,9]; 
function sumOfIndex(list , weight) { 
  weight = []; 
  for (i = 0; i < list.length; i++) {
    for (j = 0; j < list[i].length; j++) {
      list.push(weight); 
    } 
  } 
}

Answer 1

In the array from your example, the index of 6 is [3] and the index of 9 is [4] .

Simply add them together and you have 15.

Run the snippet below:

 var myArray = [1,2,4,6,9] console.log(myArray[3] + myArray[4])

Answer 2

I'd go over the array and create a map from the complement of each element to its index:

function findSum (arr, sum) {
    const diffs = new Map();
    for (let i = 0; i < arr.length; ++i) {
        if (diffs.has(arr[i])) {
            return [diffs.get(arr[i]), i];
        }
        diffs.set(sum - arr[i], i);
    }
}