704. Binary Search*

https://leetcode.com/problems/binary-search/

题目描述

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].

C++ 实现 1

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