# Binary Search Problem

## Description

LeetCode Problem 704.

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:

``````1
2
3
Input: nums = [-1,0,3,5,9,12], target = 9
Output: 4
Explanation: 9 exists in nums and its index is 4
``````

Example 2:

``````1
2
3
Input: nums = [-1,0,3,5,9,12], target = 2
Output: -1
Explanation: 2 does not exist in nums so return -1
``````

Constraints:

• 1 <= nums.length <= 10^4
• -10^4 < nums[i], target < 10^4
• All the integers in nums are unique.
• nums is sorted in ascending order.

## Sample C++ Code

``````1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
class Solution {
public:
int search(vector<int>& nums, int target) {
int n = nums.size()-1;
int low = 0, high = n;
while (low <= high) {
int mid = low + (high-low) / 2;
if (nums[mid] == target)
return mid;
else if (nums[mid] > target)
high = mid -1;
else
low = mid + 1;
}
return -1;
}
};
``````