LeetCode Search in Rotated Sorted Array

最新推荐文章于 2024-05-03 20:14:24 发布

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本文介绍了一种在旋转排序数组中查找目标值的算法实现。该算法通过递归辅助函数进行二分查找，并处理了数组旋转带来的复杂性。文章提供了一个C++类实现，包括主要搜索函数及其辅助函数。

题目：

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.

class Solution {
public:
	int search(int A[], int n, int target) {
		int ans = searchHelper(A, 0, n - 1, target);
		return ans;
	}
private:
	int searchHelper(int A[], int low, int high, int target) {
		int idx = -1;
		if(low > high)
		    return -1;
		if (A[low] <= A[high]) {
			while (low <= high) {
				int mid = (low + high) / 2;
				if (A[mid] == target) {
					idx = mid;
					break;
				}
				else if (A[mid] < target)
					low = mid + 1;
				else
					high = mid - 1;
			}
		}
		else {
			int mid = (low + high) / 2;
			if (A[mid] == target)
				idx = mid;
			else {
				idx = searchHelper(A, low, mid - 1, target);
				idx = idx == -1 ? searchHelper(A, mid + 1, high, target) : idx;
			}
		}
		return idx;
	}
};