Determine whether the values in the array are arranged in ascending or descending order

Question

Determine whether the values in the array are arranged in ascending or descending order

I'm currently working on a code problem where I need to loop over the values of an array and determine whether they are in ascending order, descending order, or neither. The function I've written so far is not giving me the correct results, but I am determined to figure out what's wrong with it.

While I have seen another approach to solving this problem, I believe that my current logic is heading in the right direction. As a learner, I want to continue exploring my own solution before resorting to alternatives. Thank you for your help!

function ascDscArray(array) {
    for (var i = 1; i < array.length - 1; i++) {
        if (array[i - 1] < array[i]) return "yes, ascending";
        if (array[i - 1] > array[i]) return "yes, descending";
        else return "no";
    }
}

Just a heads up: I'm trying to test this function with two example arrays: [15, 7, 3, -8] and [4, 2, 30].

javascript arrays loops sorting for-loop

Answer 1

Answer №1

To efficiently check the order of elements in an array, you can implement a comparison function and utilize the Array#every method with a short-circuit optimization. This approach compares each element with its preceding one to determine if they follow the expected order.

The function will return either the type of ordering (ascending or descending) or indicate if the array is not ordered at all.

function checkOrder(array) {
    var direction = array[0] < array[1]
            ? { type: 'asc', fn: (a, b) => a < b }
            : { type: 'desc', fn: (a, b) => a > b };

    return array.every((v, i, a) => !i || direction.fn(a[i - 1], v))
        ? direction.type
        : 'no';
}

console.log([[15, 7, 3, -8], [4, 2, 30], [1, 2, 3]].map(checkOrder));

An alternative version employs two variables to track ascending and descending orders separately by comparing the first element with all subsequent ones.

If both variables remain true after iteration, the function returns 'no'; otherwise, it returns the detected order.

Note: This method iterates through all elements in the array.

function detectAscDesc(array) {
    var asc = false, desc = false;
    for (var i = 1; i < array.length; i++) {
        if (array[0] < array[i]) {
            asc = true;
        }
        if (array[0] > array[i]) {
            desc = true;
        }      
    }
    if (asc && desc) return 'no';
    return asc ? 'asc' : 'desc';
}

console.log([[15, 7, 3, -8], [4, 2, 30], [1, 2, 3]].map(detectAscDesc));

Answer 2

To efficiently check the order of elements in an array, you can implement a comparison function and utilize the Array#every method with a short-circuit optimization. This approach compares each element with its preceding one to determine if they follow the expected order.

The function will return either the type of ordering (ascending or descending) or indicate if the array is not ordered at all.

function checkOrder(array) {
    var direction = array[0] < array[1]
            ? { type: 'asc', fn: (a, b) => a < b }
            : { type: 'desc', fn: (a, b) => a > b };

    return array.every((v, i, a) => !i || direction.fn(a[i - 1], v))
        ? direction.type
        : 'no';
}

console.log([[15, 7, 3, -8], [4, 2, 30], [1, 2, 3]].map(checkOrder));

An alternative version employs two variables to track ascending and descending orders separately by comparing the first element with all subsequent ones.

If both variables remain true after iteration, the function returns 'no'; otherwise, it returns the detected order.

Note: This method iterates through all elements in the array.

function detectAscDesc(array) {
    var asc = false, desc = false;
    for (var i = 1; i < array.length; i++) {
        if (array[0] < array[i]) {
            asc = true;
        }
        if (array[0] > array[i]) {
            desc = true;
        }      
    }
    if (asc && desc) return 'no';
    return asc ? 'asc' : 'desc';
}

console.log([[15, 7, 3, -8], [4, 2, 30], [1, 2, 3]].map(detectAscDesc));

Determine whether the values in the array are arranged in ascending or descending order

Answer №1

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