/***************************************************************************************

* *

* CODERBYTE BEGINNER CHALLENGE *

* *

* Arith Geo *

* Using the JavaScript language, have the function ArithGeo(arr) take the array of *

* numbers stored in arr and return the string "Arithmetic" if the sequence follows *

* an arithmetic pattern or return "Geometric" if it follows a geometric pattern. If *

* the sequence doesn't follow either pattern return -1. An arithmetic sequence is *

* one where the difference between each of the numbers is consistent, where as in a *

* geometric sequence, each term after the first is multiplied by some constant or *

* common ratio. Arithmetic example: [2, 4, 6, 8] and Geometric *

* example: [2, 6, 18, 54]. Negative numbers may be entered as parameters, 0 will not *

* be entered, and no array will contain all the same elements. *

* *

* SOLUTION *

* To check for arithmetic pattern, start by getting the difference between the first *

* two number. Then loop thru array starting in position 2 and subtract the previous *

* number. If the difference is equal to the initial difference then you have an *

* arithmetic pattern so return arithmetic. Next repeat by getting initial difference *

* by dividing the first and second numbers. Loop through array starting in position *

* 2 and compare the current number divided by previous number. If difference is *

* equal to the initial number then you have a geometric pattern. Else return -1. *

* *

* Steps for solution *

* 1) set flags for both patterns to True *

* 2) Loop thru array starting in position 2 and compare difference between current *

* number and the previous number to see if it is equal to initial difference *

* 3) If aritimetic pattern exists return arithmetic else check for geometric *

* 4) Get difference between second numvber divided by first number *

* 5) Loop thru array starting in position 2 and compare difference between current *

* number and the previous to see if it is equal to the intial difference *

* 6) If geometric pattern exists return geometric *

* 7) Else return -1 *

* *

***************************************************************************************/

function ArithGeo(arr) {

var arithFlag = true, geoFlag = true;

var diff = arr[1] - arr[0];

for (var i = 2; i < arr.length; i++) {

if ((arr[i] - arr[i-1]) !== diff) {

arithFlag = false;

}

}

if (arithFlag) {

return "Arithmetic";

}

else { // check for geometric pattern

diff = arr[1] / arr[0];

for (var i = 2; i < arr.length; i++) {

if ((arr[i] / arr[i-1]) !== diff) {

geoFlag = false;

}

}

if (geoFlag) {

return "Geometric";

}

else {

return "-1";

}

}

}