540. Single Element in a Sorted Array

这道题从中间开始找，然后看左边长度是偶数，还是奇数，往是长度是奇数的那边找

public class Solution {
    public int singleNonDuplicate(int[] nums) {
        int mid = nums.length/2;
        return findSingle(nums,0,nums.length-1);
    }

    private int findSingle(int[] nums, int start, int end) {
        int mid = (end-start)/2+start;
        if (mid == nums.length-1)return nums[nums.length-1];
        if (mid == 0)return nums[0];
        if (nums[mid-1] == nums[mid]){
            if((mid-1)%2==1){
                return findSingle(nums,start,mid-1);
            }else{
                return findSingle(nums,mid+1,end);
            }
        }else if (nums[mid+1]==nums[mid]){
            if((mid+1)%2==1){
                return findSingle(nums,mid+1,end);
            }else{
                return findSingle(nums,start,mid-1);
            }
        }else return nums[mid];
    }
}