二分查找 04

81. 搜索旋转排序数组 II.png

二分查找

class Solution {
    public boolean search(int[] nums, int target) {
        int n = nums.length;
        if (n == 0) return false;
        if (n == 1) return nums[0] == target;
        int left = 0, right = n - 1;
        while (left <= right) {
            int mid = left + (right - left) / 2;
            if (nums[mid] == target) return true;
            // cannot judge the area
            if (nums[left] == nums[mid] && nums[mid] == nums[right]) {
                left++;
                right--;
            } else if (nums[left] <= nums[mid]) {
                // left to mid area is ordered
                if (nums[left] <= target && target < nums[mid]) {
                    right = mid - 1;
                } else {
                    left = mid + 1;
                }
            } else {
                // mid to right area is ordered
                if (nums[mid] < target && target <= nums[right]) {
                    left = mid + 1;
                } else {
                    right = mid - 1;
                }
            }
        }
        return false;
    }
}