const validMountainArray = function (arr) {
let maxHeight = Number.NEGATIVE_INFINITY;
if (arr.length == 1 || arr.length === 2) {
return false;
}
for (let i = 0; i < arr.length; i++) {
maxHeight = Math.max(maxHeight, arr[i]);
}
const peakIndex = arr.indexOf(maxHeight);
if (peakIndex === 0 || peakIndex === arr.length - 1) {
return false;
}
// check up hill..
for (let i = 0; i < peakIndex - 1; i++) {
if (arr[i] >= arr[i + 1]) {
return false;
}
}
for (let i = peakIndex; i < arr.length; i++) {
if (arr[i] <= arr[i + 1]) {
return false;
}
}
return true;
};
console.log(validMountainArray([0, 1, 2, 3, 4, 5, 6, 7, 8, 9]));