direction
for the first pair of adjacent array elements.0
if the given array is empty, only has one element or the direction
changes for any pair of adjacent array elements.Math.sign()
to covert the final value of direction
to -1
(descending order) or 1
(ascending order).const isSorted = arr => {
if (arr.length <= 1) return 0;
const direction = arr[1] - arr[0];
for (let i = 2; i < arr.length; i++) {
if ((arr[i] - arr[i - 1]) * direction < 0) return 0;
}
return Math.sign(direction);
};
isSorted([0, 1, 2, 2]); // 1 isSorted([4, 3, 2]); // -1 isSorted([4, 3, 5]); // 0 isSorted([4]); // 0
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