704. Binary Search

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 targetexists, 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:

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

 

Approach #1:

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

Runtime: 52 ms, faster than 31.47% of C++ online submissions for Binary Search.