max-sum-arr.js

// // this solution uses a method called sliding window pattern
// // where we loop through the arr once and then add the next value to 
// // the current temporaly sum without also forgetting to remove the first index at 0.

// // so that arrangement is what known as sliding window pattern, with a linear time complexity.

// function maxSumArr(arr, n){
//   let maxSum = 0;
//   let tempSum = 0;

//   for(let i = 0; i < n; i++){
//       maxSum += arr[i];
//   }

//   tempSum = maxSum;
//   for(let i = n; i < arr.length; i++){
//       tempSum += arr[i] - arr[i - n];
//       maxSum = Math.max(tempSum, maxSum);
//   }

//   return (arr.length < n) ? null : maxSum;
// }

// console.log(maxSumArr([2,6,9,2,1,8,5,6,3], 3))

function countUnique(arr){
  let i = 0;
  let count = 0;

  while(i < arr.length){
    if(arr[i] !== arr[i+1]) count++;
    i++;
  }
  return count;
}

console.log(countUnique([-2,-1,-1,0,1]));
console.log(countUnique([]))