java实现二分查找

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#java #二分查找 #递归算法

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本文详细介绍了二分查找算法的实现方法，包括递归和非递归两种方式，并通过具体的Java代码示例展示了如何在已排序数组中查找指定元素的位置。

public class BinarySearch {

	public static void main(String[] args) {
		int[] a = { 1, 3, 5, 6, 7, 8, 9, 11, 12, 13 };
		System.out.println(search2(a, 1));
		System.out.println(search2(a, 3));
		System.out.println(search2(a, 5));
		System.out.println(search2(a, 6));
		System.out.println(search2(a, 7));
		System.out.println(search2(a, 8));
		System.out.println(search2(a, 9));
		System.out.println(search2(a, 11));
		System.out.println(search2(a, 12));
		System.out.println(search2(a, 13));
		System.out.println(search2(a, 100));
		System.out.println(search2(a, 10));
		System.out.println(search2(a, 0));
	}

	// 递归算法
	public static int search(int[] data, int left, int right, int des) {
		if (left > right)
			return -1;
		int middle = (left + right) / 2;
		if (des < data[middle])
			return search(data, left, middle - 1, des);
		else if (des > data[middle])
			return search(data, middle + 1, right, des);
		else
			return middle;
	}

	// 非递归算法
	public static int search2(int[] data, int des) {
		int left = 0;
		int right = data.length - 1;
		int middle = (left + right) / 2;
		while (left <= right/* && left < data.length && right >= 0 */) {
			if (data[middle] > des) {
				right = middle - 1;
				middle = (left + right) / 2;
			} else if (data[middle] < des) {
				left = middle + 1;
				middle = (left + right) / 2;
			} else
				return middle;
		}
		return -1;
	}
}