二分查找 java代码实现_二分查找代码实现java

二分查找java代码

package csdn.dreamzuora.query;

/**
 * Title: 二分查找
 * Description:
 * 时间复杂度：log2N
 * @version 1.0
 * @author: weijie
 * @date: 2020/10/16 13:52
 */
public class BinarySearch implements Search {

    int[] array;
    public BinarySearch(int[] array) {
        this.array = array;
    }

    @Override
    public int search(int data) {
        int startIndex = 0;
        int endIndex = array.length - 1;
        int midIndex = startIndex + (endIndex - startIndex) / 2;
        while (midIndex >= startIndex && midIndex <= endIndex){
            if (array[midIndex] == data){
                return midIndex;
            }
            if (data > array[midIndex]){
                startIndex = midIndex + 1;
            }else {
                endIndex = midIndex - 1;
            }
            midIndex = startIndex + (endIndex - startIndex) / 2;
        }
        return -1;
    }
}

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单元测试

package csdn.dreamzuora.query;

import org.junit.Test;
import org.junit.jupiter.api.Assertions;

import static org.junit.Assert.*;

/**
 * Title:
 * Description:
 *
 * @version 1.0
 * @author: weijie
 * @date: 2020/10/16 14:00
 */
public class BinarySearchTest {

    @Test
    public void search() {
        int[] array = new int[10];
        for (int i = 0; i < 10; i++){
            array[i] = i;
        }
        BinarySearch binarySearch = new BinarySearch(array);
        Assertions.assertEquals(3, binarySearch.search(3));
        Assertions.assertEquals(8, binarySearch.search(8));
        Assertions.assertEquals(0, binarySearch.search(0));
        Assertions.assertEquals(9, binarySearch.search(9));
    }
}
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