LeetCode #704: Binary Search (C/C++).

easy

source: https://leetcode.com/problems/binary-search
C/C++ Solution to LeetCode problem 704. Binary Search.

Problem

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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.

Examples

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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

Constraints

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• 1 <= nums.length <= 104
• -104 < nums[i], target < 104
• All the integers in nums are unique.
• nums is sorted in ascending order.

Solution

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class Solution {
public:
  int search(vector<int>& nums, int target) {
    int low = 0;
    int high = nums.size() - 1;
    int mid;

    while (low <= high) {
      mid = (low + high) / 2;

      if (nums[mid] == target)
        return mid;
            
      if (nums[mid] > target)
        high = mid - 1;
      else
        low = mid + 1;
    }

    return -1;   
  }
};