LeetCode 33. Search in Rotated Sorted Array

描述

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.

分析

二分查找，难度主要在于左右边界的确定。

代码

class Solution {
public:
int search(vector<int>& nums, int target) {
int first = 0;
int last = nums.size();

while (first != last) {
int mid = (first + last) / 2;

if (nums[mid] == target)
return mid;

if (nums[first] <= nums[mid]) {
if (nums[first] <= target && target < nums[mid])
last = mid;
else
first = mid + 1;
}
else {
if (nums[mid] < target && target <= nums[last - 1])
first = mid + 1;
else
last = mid;
}
}
return -1;
}
};