LeetCode - Easy - 704. Binary Search-蒲公英云

LeetCode - Easy - 704. Binary Search

Topic

Binary Search

Description

https://leetcode.com/problems/binary-search/

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.

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:

1 < = n u m s . l e n g t h < = 1 0 4 1 <= nums.length <= 10^4 1<=nums.length<=104
− 9999 < = n u m s [ i ] , t a r g e t < = 9999 -9999 <= nums[i], target <= 9999 −9999<=nums[i],target<=9999
All the integers in nums are unique.
nums is sorted in an ascending order.

Analysis

Submission

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

Test

import static org.junit.Assert.*;
import org.junit.Test;
public class BinarySearchTest { 
    @Test
    public void test() { 
        BinarySearch obj = new BinarySearch();
        assertEquals(4, obj.search(new int[] {  -1, 0, 3, 5, 9, 12 }, 9));
        assertEquals(-1, obj.search(new int[] {  -1, 0, 3, 5, 9, 12 }, 2));
        assertEquals(0, obj.search(new int[] { 5}, 5));
    }
}