704. Binary Search

704. Binary Search (Easy)

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:

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].

Related Topics:
Binary Search

Similar Questions:

• Search in a Sorted Array of Unknown Size (Medium)

Solution 1.

// OJ: https://leetcode.com/problems/binary-search/
// Author: github.com/lzl124631x
// Time: O(logN)
// Space: O(1)
class Solution {
public:
    int search(vector<int>& A, int target) {
        int L = 0, R = A.size();
        while (L <= R) {
            int M = (L + R) / 2;
            if (A[M] == target) return M;
            if (A[M] < target) L = M + 1;
            else R = M - 1;
        }
        return -1;
    }
};