704. Binary Search

最新推荐文章于 2024-04-18 11:27:57 发布

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最新推荐文章于 2024-04-18 11:27:57 发布

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分类专栏： LeetCode

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博客围绕在升序整数数组中查找特定值展开，介绍了编写函数进行查找的需求，若值存在则返回其索引，不存在则返回特定值，还给出了示例，并提及数组元素唯一等注意事项，最后给出二分查找程序。

Given a sorted (in ascending order) integer array nums of n elements and a target value, write a function to search target in nums. If target exists, then return its index, otherwise return -1.
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

Note:

You may assume that all elements in nums are unique.
n will be in the range [1, 10000].
The value of each element in nums will be in the range [-9999, 9999].

二分查找，程序如下所示：

class Solution {
    public int search(int[] nums, int target) {
        int left = 0, right = nums.length - 1;
        while (left <= right){
            int mid = left + ((right - left) >> 1);
            if (target == nums[mid]){
                return mid;
            }
            else if (target < nums[mid]){
                right = mid - 1;
            }
            else {
                left = mid + 1;
            }
        }
        return -1;
    }
}