LC/33.search-in-rotated-sorted-array.cpp at master · suyuee/LC · GitHub

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/*
 * @lc app=leetcode id=33 lang=cpp
 *
 * [33] Search in Rotated Sorted Array
 *
 * https://leetcode.com/problems/search-in-rotated-sorted-array/description/
 *
 * algorithms
 * Medium (33.00%)
 * Total Accepted:    437.1K
 * Total Submissions: 1.3M
 * Testcase Example:  '[4,5,6,7,0,1,2]\n0'
 *
 * Suppose an array sorted in ascending order is rotated at some pivot unknown
 * to you beforehand.
 *
 * (i.e., [0,1,2,4,5,6,7] might become [4,5,6,7,0,1,2]).
 *
 * You are given a target value to search. If found in the array return its
 * index, otherwise return -1.
 *
 * You may assume no duplicate exists in the array.
 *
 * Your algorithm's runtime complexity must be in the order of O(log n).
 *
 * Example 1:
 *
 *
 * Input: nums = [4,5,6,7,0,1,2], target = 0
 * Output: 4
 *
 *
 * Example 2:
 *
 *
 * Input: nums = [4,5,6,7,0,1,2], target = 3
 * Output: -1
 *
 */
class Solution {
public:
    int search(vector<int>& nums, int target) {
        int l = 0, r = nums.size() - 1;
        while (l <= r) {
            int mid = l + (r - l) / 2;
            if (nums[mid] == target)
                return mid;
            if (nums[mid] > target) {
                if (nums[mid] > nums[r]) {
                    if (nums[r] >= target)
                        l = mid + 1;
                    else
                        r = mid - 1;
                }
                else
                    r = mid - 1;
            }
            else {
                if (nums[mid] > nums[r])
                    l = mid + 1;
                else {
                    if (nums[r] >= target)
                        l = mid + 1;
                    else
                        r = mid - 1;
                }
            }
        }
        return -1;
    }
};