LeetCode-33. Search in Rotated Sorted Array

[ninehills]

问题

https://leetcode.com/problems/search-in-rotated-sorted-array/description/
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.

思路

• 顺序查找就不说了，最优解应该是二分查找的一个变种，主要是考虑边界条件

解答

package main

import "fmt"

// ----------------------
func search(nums []int, target int) int {
	var l int = 0
	var r int = len(nums) - 1
	if r < 0 {
		return -1
	}
	for l < r {
		m := (l + r) / 2
		if nums[m] == target {
			return m
		}
		if nums[m] >= nums[l] {
			if target < nums[m] && target >= nums[l] {
				r = m - 1
			} else {
				l = m + 1
			}
		} else {
			if target > nums[m] && target <= nums[r]{
				l = m + 1
			} else {
				r = m - 1
			}
		}
	}
	if nums[l] == target {
		return l
	} else {
		return -1
	}
}

// ----------------------

func main() {
	fmt.Println(search([]int{1, 3}, 0))
	fmt.Println(search([]int{}, 5))
	fmt.Println(search([]int{4, 5, 6, 7, 0, 1, 2}, 1))
	fmt.Println(search([]int{4, 5, 6, 7, 8, 1, 2, 3}, 8))
}

[ninehills]

#4