Leetcode 704. Binary Search

Given a sorted (in ascending order) integer array nums of n elements and a targetvalue, 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].

Difficulty:Medium

Category:

Solution

Time complexity: O(log n) Space complexity: O(1)

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