[Leetcode] Find Peak Element

A peak element is an element, which is greater than its neighbors.


Given an input array where num[i]≠num[i+1], find a peak element and return its index.


The array may be contain multiple peaks, in this case return the index to any one of the peaks is fine.


Imagine that num[-1] = num[n] =-∞.


For example, in array [1, 2, 3, 1], 3 is a peak element and your function should return the index number 2.

Idea 1: Traversal, O (N)
Code Listing 1:

    public int findPeakElement1 (int[] num) {//Violence for        (int i = 0; i < num.length; ++i) {            if (I+1 < num.length)                { if (Num[i] > Num[i+1] && ((i-1 >= 0 && num[i] > num[i-1]) | | (I-1 < 0))) {                    return i;                }            } else {                if (i-1 < 0 | | i-1 >=0 && num[i] > Num[i-1]) {                    return i;}}        }        return 0;    }

Idea 2: two points,
Code:

    public int findpeakelement (int[] num) {//        int l = 0, R = num.length-1, mid;        while (L < R) {            mid = L + (r-l)/2;            if (Num[mid] < Num[mid + 1]) L = mid + 1;            else R = Mid;        }        return num[l];    }

[Leetcode] Find Peak Element