LeetCode: 33. 搜索旋转排序数组

[resse92]

二分查找法，注意左右边界的确定。

class Solution {
public:
    int search(vector<int>& nums, int target) {
        int first = 0, last = nums.size();
        
        while (first != last) {
            const int mid = (first + last) / 2;
            if (nums[mid] == target) {
                return mid;
            } else 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;
    }
};