[LeetCode]Search in Rotated Sorted Array
题目描述:(链接)
Suppose a sorted array 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.
解题思路:
二分查找，分三种情况讨论，找个例子，例如（0,1,2,3,4），把所有的旋转情况都画出来就可以了，主要是边界比较难确定。
class Solution {
public:
int search(vector<int>& nums, int target) {
size_t first = 0;
size_t last = nums.size();
while (first != last) {
size_t mid = first + (last - first) / 2;
if (nums[mid] == target) {
return mid;
} else if (nums[mid] >= nums[first]) {
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;
}
};