LeetCode Find Peak Element

链接: https://oj.leetcode.com/problems/find-peak-element/

题目要求复杂度在对数级以内

对数组下标进行二分搜索,

public class Solution
{
	public int findPeakElement(int [] num)
	{
		int l=0,r=num.length-1;
		int mid=(l+r)/2;
		while(r-l>1)										//按下标二分搜索
		{
		    mid=(l+r)/2;
			if(num[mid-1]<num[mid]&&num[mid]>num[mid+1])		
				return mid;
			if(num[mid-1]>num[mid+1])
			{
				r=mid;
				continue;
			}
			if(num[mid-1]<num[mid+1])
			{
				l=mid;
				continue;
			}
		    if(num[mid-1]==num[mid+1])
			{
			    if(l==0)
			    {
			        if(num[l]>num[l+1])
			            return l;
			        else
			            {
			                l++;
			                continue;
			            }
			    }
			    if(l!=0)
			    {
			        if(num[l-1]<num[l]&&num[l]>num[l+1])
			            return l;
			        else
			        {
			            l++;
			            continue;
			        }
			    }
			        
			}
		}
		return num[l]>num[r]?l:r;
	}
}