package com.algorithm.sort;

import org.junit.Assert;

import org.junit.Test;

/**

* @author chen_wj

* @Description:

* @date 2019/11/5

* @Description: 二分查找算法

* @modifier

*/

public class BiSearch {

@Test

public void testBiSearch() {

int[] arr = {1,3,4,5,7,9,11,15,20};

Assert.assertEquals(biSearch(arr,1), 0);

Assert.assertEquals(biSearch(arr,4), 2);

Assert.assertEquals(biSearch(arr,15), 7);

Assert.assertEquals(biSearch(arr,20), 8);

Assert.assertEquals(biSearch(arr,6), -1);

}

public static int biSearch(int[] arr, int target) {

int min = 0;

int max = arr.length - 1;

int mid;

while(min <= max) {

mid = (min + max) / 2;

if (arr[mid] == target) {

return mid;

} else {

if (arr[mid] > target) {

max = mid - 1;

} else {

min = mid + 1;

}

}

}

return -1;

}

}