Description
Given an array of integers nums which is sorted in ascending order, and an integer target, write a function to search target in nums. If target exists, then return its index. Otherwise, return -1.
You must write an algorithm with O(log n) runtime complexity.
Examples
Example 1:
Input: nums = [-1,0,3,5,9,12], target = 9
Output: 4
Explanation: 9 exists in nums and its index is 4
Example 2:
Input: nums = [-1,0,3,5,9,12], target = 2
Output: -1
Explanation: 2 does not exist in nums so return -1
Constraints:
1 <= nums.length <= 1 0 4 10^4 104
? 1 0 4 -10^4 ?104 < nums[i], target < 1 0 4 10^4 104
All the integers in nums are unique.
nums is sorted in ascending order.
思路
二分查找
代码
class Solution {
public int _search(int[] nums, int start, int end, int target) {
if (start > end)
return -1;
int mid = (start + end) / 2;
if (nums[mid] == target)
return mid;
if (nums[mid] < target)
return _search(nums, mid + 1, end, target);
return _search(nums, start, mid - 1, target);
}
public int search(int[] nums, int target) {
return _search(nums, 0, nums.length - 1, target);
}
}
