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LeetCode – Easy – 704. Binary Search

1周前 (04-08) 8次浏览

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.

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));
}
}
``````

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