二分查找

package com.mycom.test;

public class BinarySearch {

	public static int bs(int a[], int tag) {
		int first = 0;
		int end = a.length;
		for (int i = 0; i < a.length; i++) {
			int middle = (first + end) / 2;
			if (tag == a[middle]) {
				return middle;
			}
			
			if (tag > a[middle]) {
				first = middle + 1;
			}

			if (tag < a[middle]) {
				end = middle - 1;
			}
		}

		return 0;

	}

	public static void main(String[] args) {
		int[] a = {1,3,6,7,9,11};
		System.out.println(bs(a, 6));
	}

}