【数据结构与算法】二分查找

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基本思想

首先将给定的值K与表中中间位置元素比较，若相等，则查找成功；若不等，则所需查找的元素只能在中间数据以外的前半部分或者后半部分，缩小范围后继续进行同样的查找，如此反复，直到找到为止。

代码实现

/** * 源码名称：BinarySearch.java  * 日期：2014-08-14  * 程序功能：二分查找  * 版权：CopyRight@A2BGeek * 作者：A2BGeek */public class BinarySearch {public static int binarySearch(int[] in, int key) {int start = 0;int end = in.length - 1;int index = -1;while (start <= end) {// int mid = (start + end) / 2;会溢出// int mid = start + (end - start) / 2;int mid = start + ((end - start) >> 2);// int mid = (start + end) >>> 1;if (key < in[mid]) {end = mid - 1;} else if (key > in[mid]) {start = mid + 1;} else {index = mid;break;}}return index;}public static int binarySearchRecursive(int[] in, int key, int start,int end) {if (start <= end) {int mid = start + ((end - start) >> 2);if (key < in[mid]) {end = mid - 1;return binarySearchRecursive(in, key, start, end);} else if (key > in[mid]) {start = mid + 1;return binarySearchRecursive(in, key, start, end);} else {return mid;}} else {return -1;}}public static void main(String[] args) {int[] testCase = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 13, 15, 20, 36 };System.out.println(binarySearch(testCase, 12));System.out.println(binarySearchRecursive(testCase, 12, 0,testCase.length - 1));}}

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