Question

How to replace every element in array by multiplication of next and previous elements with JavaScript

Answer 1

// arr[first] = arr[first] (itself) * arr[next];
// arr[last] = prev * arr[last] (itself);

function MultiplyNextPrevious(arr) {
    const size = arr.length;
    
    if (size <= 1) {
        return;
    }
    
    let prev = arr[0];
    arr[0] = arr[0] * arr[1];
    
    for (let i = 1; i < size - 1; i++) {
        let curr = arr[i];
        arr[i] = prev * arr[i + 1]; // arr[i + 1] = next
        prev = curr;
    }
    arr[size - 1] = prev * arr[size - 1];
}
        
const arr = [2, 3, 5, 6, 12, 8, 10, 7];
        
MultiplyNextPrevious(arr);

for (let i = 0; i < arr.length; i++) {
    console.log(arr[i]);
}




/*
run:

6
10
18
60
48
120
56
70

*/

 

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