Binary Search | LeetCode 704 | C

2023-09-05
#LeetCode #C #Array #Binary Search
LeetCode

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:

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

Example 2:

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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.

Approach

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Use binary search to find the target.

Algorithm

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Use binary search to find the target.

Implementation

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int search(int* nums, int numsSize, int target){
    int low= 0, high = numsSize -1, mid = 0;
    while(low <= high){
        mid = low + (high - low)/2;
        if(nums[mid] > target)
            high = mid - 1;
        else if (nums[mid] < target)
            low = mid + 1;
        else
            return mid;
    }
    return -1;
}