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:
- $1 <= nums.length <= 10^4$
- $-9999 <= nums[i], target <= 9999$
- 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));
}
}