October 05, 2019

33. Search in Rotated Sorted Array

33. Search in Rotated Sorted Array

参考这个视频. Time = O(log(n)), Space = O(1)

class Solution {
    public int search(int[] nums, int target) {
        if (nums == null || nums.length == 0) {
            return -1;
        }
        int left = 0;
        int right = nums.length - 1;
        while (left <= right) {
            int mid = left + (right - left) / 2;
            if (nums[mid] == target) {
                return mid;
            } else if (nums[mid] < nums[left]) { // left half is rotated, right half is sorted
                if (target > nums[mid] && target <= nums[right]) {
                    left = mid + 1;
                } else {
                    right = mid - 1;
                }
            } else { // right half is rotated, left half is sorted
                if (target < nums[mid] && target >= nums[left]) {
                    right = mid - 1;
                } else {
                    left = mid + 1;
                }
            }
        }
        return -1;
    }
}
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