count consecutive number

count consecutive numbers.js

const arr = [-1, -1, 1, 1, 1, 1, 7, 11, 11];

// [ -1, 2, 1, 4, 7, 1, 11, 2];

class Stack {
	constructor() {
		this.values = [];
	}

	push(v) {
		this.values.push(v);
	}

	pop() {
		return this.values.pop();
	}

	peek() {
		return this.values[this.values.length - 1];
	}

	isEmpty() {
		return this.values.length == 0;
	}
}

function countFrequency(arr) {
	let stack = new Stack();
	let answer = [], count, currentElementInStack, element;

	for (let i = 0; i <= arr.length; i++) {
		element = arr[i];

		if ((stack.peek() != element) && !stack.isEmpty()) {
			//start poping and clear the stack
			count = 0; 
			currentElementInStack = stack.peek();
			while(!stack.isEmpty()) {
				stack.pop();
				count++;
			}
			answer.push(currentElementInStack);
			answer.push(count);
		}
		stack.push(element);
	}
	return answer;
}

console.log( countFrequency(arr));

[ -1, 2, 1, 4, 7, 1, 11, 2 ]
[Finished in 0.1s]