Leetcode 704. Binary Search C++

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最新推荐文章于 2025-05-29 23:36:29 发布

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本文介绍了一种高效的搜索算法——二分查找（Binary Search），用于在已排序的整数数组中查找目标值。该算法的时间复杂度为O(log n)，适用于解决在有序数据中查找特定元素的问题。通过实例和代码实现，理解其工作原理并应用于实际编程场景。

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704. Binary Search

Easy

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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.

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

class Solution {
public:
    int search(vector<int>& nums, int target) {
        int low = 0, high = nums.size()-1;
        while (low <= high){
            int middle = (low+high)/2;
            if (nums[middle] == target){
                return middle;
            }
            else if (nums[middle]> target) high = middle-1;
            else low = middle+1;
        }
        return -1;
    }
};