Question 11233 in Jquery Question posted in
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Find position of Paired Numbers in Array – Jquery

let input arr=[9,4,4,8,90,4,9,4,4,4,4,4,4,4,4,4,7,9,2,4,4,4,4,4,8,4,4,4,4];

let output arr=[1,7,9,11,13,15,19,21,25,27];

Above is an input array of numbers which contain mostly 4, if there is a pair of 4 which means (Input elements has 2 of the number 4 consecutively), its array position will be displayed in the output array. I have tried my code below but I am still unsure on how to solve this :). May I know how to solve this?

console.clear();
let arr=[8,4,4,4,4,4,4,4,4,4,7,9,2,4,4,4,4,4,8,4,4,4,4];

console.log("his")
for (let i=0;i<arr.length;i++){
if (arr[i]!==arr[i+1] &&arr[i]!==4 ){
console.log(i)
}
if (arr[i]!==arr[i+1] &&arr[i+1]!==4 ){
console.log(i+1)
}

}
Tags:

2

Answers


  1. 0

    You could look to the next item and if the last index is not in the result array, the add the actual index to the result.

    const
    input = [9, 4, 4, 8, 90, 4, 9, 4, 4, 4, 4, 4, 4, 4, 4, 4, 7, 9, 2, 4, 4, 4, 4, 4, 8, 4, 4, 4, 4],
    result = input.reduce((r, v, i, a) => {
        if (v === a[i + 1] && r[r.length - 1] !== i - 1) r.push(i);
        return r;
    }, []);

console.log(...result);

    An approach for n elements with a closure over a counting variable c.

    const
    getIndices = (array, n) => input.reduce((c => (r, v, i, a) => {
        if (!c) {
            if (v === a[i + 1]) c = 1;
            return r;
        }

        c = v === a[i - 1] ? c + 1 : 0;
        
        if (c === n) {
            r.push(i - n + 1);
            c = 0;
        }
        return r;
    })(0), []),
    input = [9, 4, 4, 8, 90, 4, 9, 4, 4, 4, 4, 4, 4, 4, 4, 4, 7, 9, 2, 4, 4, 4, 4, 4, 8, 4, 4, 4, 4];

console.log(...getIndices(input, 2));
console.log(...getIndices(input, 3));
console.log(...getIndices(input, 4));
console.log(...getIndices(input, 5));
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  2. 0

    This is a possible solution:

    console.clear();
let arr=[8,4,4,4,4,4,4,4,4,4,7,9,2,4,4,4,4,4,8,4,4,4,4];
let pair = false;

for (let i=0;i<arr.length;i++){
  if (pair == false) {
      if (arr[i]==arr[i+1]){
        console.log(i)
        pair = true; // show that we have found a pair
      }              // thus we skip a 'for' loop
  }
  else {
    pair = false; // reset the pair variable
  }
}

    output: [1, 3, 5, 7, 13, 15, 19, 21]

    Do you want this pair:
    let arr=[8,4,4,4,4,4,4,4,4,4,7,9,2,4,4,4,4,4,8,4,4,4,4];

    to be counted, as well?

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