basicsorttool.java

来自「<算法导论>第二版大部分算法实现. 1. 各类排序和顺序统计学相关」· Java 代码 · 共 96 行

/*
 * Copyright (C) 2000-2007 Wang Pengcheng <[e-mail]>
 * Licensed to the Wang Pengcheng under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The LGPL licenses this file to You under the GNU Lesser General Public
 * Licence, Version 2.0  (the "License"); you may not use this file except in
 * compliance with the License.  You may obtain a copy of the License at
 *
 *     http://www.gnu.org/licenses/lgpl.txt
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
//15 Oct 2007
package cn.edu.whu.iss.algorithm.basictools;

import java.util.Random;

public final class BasicSortTool {
	
	/**
	 * For random a integer
	 */
	private static Random rand = new Random();
	
	/**
	 * Compare two objects.
	 * @param o1
	 * @param o2
	 * @return a integer <0(o1<o2) =0(o1=o2) >0(o1>o2) 
	 * 
	 */
	public static int compare(Object o1,Object o2){
		if(o1==null&&o2!=null){
			return -1;
		}else if(o1!=null&&o2==null){
			return 1;
		}else{
			return ((Comparable)o1).compareTo(o2);
		}
	}
	
	/**
	 * Get a integer between l and r
	 * @param l
	 * @param r
	 * @return
	 */
	public static int randomInt(int l,int r){
		if(r<l){
			int t=r;
			r=l;
			l=t;
		}
		if(r==l){
			return l;
		}else{
			return rand.nextInt(r-l)+l;
		}
	}
	
	/**
	 * Swap two elements in the array.And the elements is the i and j.
	 * @param o element array
	 * @param i one element
	 * @param j other one
 	 */
	public static void swap(Object[] o,int i,int j){
		Object temp = o[i];
		o[i] = o[j];
		o[j] = temp;
	}
	
	/**
	 * Get the max value in the elements array.
	 * @param element array
	 * @return the max value
	 */
	public static Object max(Object[] element){
		if( (element==null)||(element.length==0)){
			return null;
		}
		int k=0;
		for(int i=1;i<element.length;i++){
			if(compare(element[i], element[k])>0){
				k=i;
			}
		}
		return element[k];
	}
}