## Binary Search - 33. Search in Rotated Sorted Array

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33. Search in Rotated Sorted Array

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
``````

go：

``````func search(nums []int, target int) int {

if nums == nil || len(nums) == 0 {
return -1
}

left := 0
right := len(nums)-1

for left <= right {
mid := left + (right - left) / 2
if nums[mid] == target {
return mid
} else if nums[mid] < nums[left]  {
// 左边是rotated sorted array
if target > nums[mid] && target <= nums[right] {
left = mid + 1
} else {
right = mid - 1
}
} else {
// 右边是rotated sorted array 左边是sorted array
if target < nums[mid] && target >= nums[left] {
right = mid - 1
} else {
left = mid + 1;
}
}
}

return -1
}
``````