binary search-优快云博客

本文介绍了一种在升序排列的整数数组中查找特定元素的二分查找算法实现。该算法通过不断缩小搜索范围来提高查找效率，并返回目标元素在数组中的位置索引。

摘要生成于 C知道，由 DeepSeek-R1 满血版支持，前往体验 >

binary search in sorted array:

package me.util.algorithm;

/**
 * binary search util
 * @author eric
 * @date 2010-8-29 下午07:09:41
 */
public class BinarySearchUitl {

	public static void main(String[] args) {
		int[] is = new int[] { -10, -9, -9, -5, -4, -3, -3, -2, -1, 0, 1, 2, 5, 6, 7, 8, 9, 11, 14 };
		System.out.println(locateNumInSortedArray(-5, is));
		System.out.println(locateNumInSortedArray(4, is));
	}

	/**
	 * locate num in a sorted array
	 * @param num number to locate
	 * @param arr sorted array in asc order
	 * @return index of the num in array.If not find,-1 will be return.
	 */
	public static int locateNumInSortedArray(int num, int[] arr) {
		if (arr.length == 0 || arr[0] > num || arr[arr.length - 1] < num) {
			return -1;
		}

		int startIndex = 0, endIndex = arr.length - 1;
		while (startIndex <= endIndex) {
			int middleIndex = (startIndex + endIndex) >> 1;
			if (num == arr[middleIndex]) {
				return middleIndex;
			} else if (num > arr[middleIndex]) {
				startIndex = middleIndex + 1;
			} else {
				endIndex = middleIndex - 1;
			}
		}
		return -1;
	}
}