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A few math magic #1

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39 changes: 14 additions & 25 deletions easy/arith_geo.js
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Original file line number Diff line number Diff line change
Expand Up @@ -15,35 +15,24 @@
* @return {string} or -1 on failure
*/
function arithGeo(arr) {
if (arr.length === 1 || arr.length === 0) {
return -1;
}

let arithmetic = true;
// test arithmetic
for (let i = 2, diff = arr[1] - arr[0]; i < arr.length; i++) {
if (arr[i] - arr[i - 1] !== diff) {
arithmetic = false;
}
}
if (arr.length === 1 || arr.length === 0) {
return -1;
}

if (arithmetic) {
return 'Arithmetic';
}
//geo: a1, a1*r, a1*r**2, a1*r**3
//art: a1, a1+1, a1+2r, a1+3r

let geometric = true;
// geometric
for (let i = 2, divisor = arr[1] / arr[0]; i < arr.length; i++) {
if (arr[i] / arr[i - 1] !== divisor) {
geometric = false;
}
}
let r = Math.floor(arr[1] / arr[0]);

if (geometric) {
return 'Geometric';
}
for (let i = 2; i < arr.length; i++) {
if (arr[i] === arr[0] * r * r) return "Geometric";
else return "Arithmetic";
}

return -1;
return -1;
}

// let result = arithGeo([2, 4, 6, 8])
// console.log(result)

module.exports = arithGeo;