Arithmetic Slice

Arithmetic Slice.js

/* 
* Returns the number of arithmetic slices in 
* the given number array. 
* 
* Examples: 
* [-1, 1, 3, 3, 3, 2, 1, 0]  = 5 
* 
* A sequence is an Arithmetic if: 
*  1. It consists of 3 elements
*  2. The difference between any two consecutive
*      elements is the same
*/
function solution(A) {
    
    var result = 0;
    var dp = 0;
    // Iterate through the elements
    for (var i=2;i< A.length; i++){
        // Check the sequence of numbers if they pass as Arithmetic
        if ((A[i-1]-A[i-2]) == (A[i]-A[i-1])){  
            dp=1 + dp;
            result += dp;
        } else{
            dp = 0;
        }
    }
    
    // Returns -1 if result exceeds to 1 Billion
    return (result > 1000000000) ? -1 : result;
    
}