Question

How to check if a sequence of numbers is a Harmonic progression (reciprocals Arithmetic progression) in Node.js

Answer 1

// a, b, c, d are HP if 1/a, 1/b, 1/c, 1/d are AP -> 1/a, 1/(a+diff), 1/(a+2*diff)...

function isHarmonicProgression(arr) {
    const size = arr.length;
    if (size === 1) return 1;

    const difference = (1.0 / arr[1]) - (1.0 / arr[0]);

    for (let i = 2; i < size; i++) {
        if ((1.0 / arr[i]) - (1.0 / arr[i - 1]) !== difference) {
            return 0; 
        }
    }

    return 1; 
}

const arr = [1.0 / 5, 1.0 / 10, 1.0 / 15, 1.0 / 20, 1.0 / 25, 1.0 / 30]; 

console.log(isHarmonicProgression(arr) === 1 ? "Yes" : "No");




/*
run:

Yes

*/

 

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