LeetCode - 852. 山脉数组的峰顶索引
/**
* @param {number[]} A
* @return {number}
*/
var peakIndexInMountainArray = function(A) {
let top = -1;
for(let i = 1; i < A.length; i++){
if(A[i] >= A[i-1]){
continue;
}else{
top = i-1;
break;
}
}
return top;
};