704.Binary Search

发表于 | 分类于 ， | 评论数： | 阅读次数：
字数统计: 162 | 阅读时间 ≈ 1

题目描述

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

我的解法

实现代码

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
class Solution {
public:

    int search(vector<int>& nums, int target) {
        int left = 0;
        int right= nums.size()-1;
        while(left <= right){
            int mid = (right - left) / 2 + left;
            if (nums[mid] == target)
                return mid;
            if (nums[mid] < target)
                left = mid + 1;
            if (nums[mid] > target)
                right = mid - 1;
        }
        return -1;
    }
};