540. 有序数组中的单一元素

二分

class Solution {
    public int singleNonDuplicate(int[] nums) {
        int size = nums.length;
        if(size == 1) return nums[0];
        int left = 0, right = size -1;
        //正常情况下偶数是第一个元素
        while (left < right ) {
            int mid = left + ( (right - left) >> 1);
            if( (mid & 1) == 0 ){
                if(nums[mid] == nums[mid + 1]) {
                    left = mid + 1;
                } else {
                    right = mid;
                }
            } else {
                if(nums[mid] == nums[ mid - 1] ) {
                    left = mid + 1;
                } else {
                    right = mid;
                }
            }
        }
        return nums[right];
    }
}

class Solution {
    public int singleNonDuplicate(int[] nums) {
        int size = nums.length;
        if(size == 1) return nums[0];
        int left = 0, right = size -1;
        //正常情况下偶数是第一个元素
        while (left < right ) {
            int mid = left + ( (right - left) >> 1);
            if( (mid & 1) == 0 ){
                if(nums[mid] == nums[mid + 1]) {
                    //[1,1,2,2,3] left = mid + 2
                    left = mid + 2;
                } else {
                    right = mid;
                }
            } else {
                //[1,1,2] left + 1
                if(nums[mid] == nums[ mid - 1] ) {
                    left = mid + 1;
                } else {
                    right = mid;
                }
            }
        }
        return nums[right];
    }
}

亦或

class Solution {
    public int singleNonDuplicate(int[] nums) {
        int left = 0,right = nums.length - 1;
        while (left < right ) {
            int mid = left + ((right - left) >> 1 );
            //!!!偶数亦或1 等于 加1
            //!!!奇数亦或1 等于 减1
            if(nums[mid] == nums[mid ^ 1]) {
                left = mid + 1;
            } else {
                right = mid ;
            }
        }
        return nums[right];
    }
}