Given a non-empty array containing only non-negative integers, return the list with trailing and leading zeroes removed.

issue-298-of-rendezvous-with-cassidoo.ts

import { equal } from "https://deno.land/x/equal/mod.ts";

function getArrayWithZeroesRemoved(arr, startIndex, endIndex) {
    const arrayWithZeroesRemoved = new Array(endIndex - startIndex + 1);
    let i = 0;
    while (startIndex <= endIndex) {
        arrayWithZeroesRemoved[i] = arr[startIndex];
        i++;
        startIndex++;
    }

    return arrayWithZeroesRemoved;
}

// O(n) time & O(n) space - where n is the length of the input array
export default function removeZeroes(arr: number[]): number[] {
    let leftPointer = 0;
    let rightPointer = arr.length - 1;
    let startIndex = leftPointer;
    let endIndex = rightPointer;
    let startIndexFound = false;
    let endIndexFound = false;
    while (leftPointer <= rightPointer) {
        if (arr[leftPointer] !== 0 && !startIndexFound) {
            startIndex = leftPointer;
            startIndexFound = true;
        }
        if (arr[rightPointer] !== 0 && !endIndexFound) {
            endIndex = rightPointer;
            endIndexFound = true;
        }
        if (startIndexFound && endIndexFound) {
            return getArrayWithZeroesRemoved(arr, startIndex, endIndex);
        }
        if (!endIndexFound) {
            rightPointer--;
        }
        if (!startIndexFound) {
            leftPointer++;
        }
    }

    return [];
}

console.assert(equal(removeZeroes([0, 0, 0, 3, 1, 4, 1, 5, 9, 0, 0, 0, 0]), [3, 1, 4, 1, 5, 9]));
console.assert(equal(removeZeroes([0, 0, 0]), []));
console.assert(equal(removeZeroes([8]), [8]));
console.assert(equal(removeZeroes([0, 3, 0, 4, 0]), [3, 0, 4]));
console.assert(equal(removeZeroes([0, 3, 4]), [3, 4]));
console.assert(equal(removeZeroes([3, 4, 0]), [3, 4]));
console.assert(equal(removeZeroes([3, 4]), [3, 4]));
console.assert(equal(removeZeroes([2, 3, 4]), [2, 3, 4]));
console.assert(equal(removeZeroes([0]), []));
console.assert(equal(removeZeroes([0, 0, 0, 1, 23]), [1, 23]));
console.assert(equal(removeZeroes([22, 2, 0, 0]), [22, 2]));