剑指offer刷题之java实现的把数组排成最小的数

题目描述

import java.util.Arrays;
import java.util.Comparator;

public class PrintMinNumberSolution {
	//方法一：用comparable接口实现
    public String PrintMinNumber(int [] numbers) {
    	 String res = "";
         if(numbers==null || numbers.length == 0){
           return res;
         }
		MString m[] = new MString[numbers.length];
    	String st[] = Int2String(numbers);
    	int k=0;
    	for(String i:st){
    		m[k] = new MString();//！必须先赋值才能对它的成员变量进行访问
    		m[k++].s = i;
    	}
    	Arrays.sort(m);
    	for (int i = 0; i < m.length; i++) {
    		res+=m[i].s;
		}
		return res;
    }
  //方法一 ：必须要对进行比较的类T内部进行改造。首先实现接口 Comparable<T>，（必须是T因为后面比较内部都是对对象进行的，否则出现类型转换错误）
  //然后重写方法 compare(T t)即可。然后Arrays.sort(T[])自动回调用这个比较器
    class MString implements Comparable<MString>{
    	public String s ;
    	@Override
    	public int compareTo(MString o) {
    		// TODO Auto-generated method stub
    		String s1 = s+o.s;
    		String s2 = o.s+s;
    		if(s1.compareTo(s2) > 0){
    			return 1;
    		}else if(s1.compareTo(s2) <0)
    			return -1;
    		else return 0;
    	}
    	public String toString() {  
            return s;//"MString [s=" + s + "]";  
        } 
    }
    public String[] Int2String(int [] a){
    	String b[] = new String[a.length];
    	for(int i=0;i<a.length;i++){
    		b[i] = String.valueOf(a[i]);
    	}
//    	System.out.println(Arrays.toString(b));
    	return b;
    }

  //方法二：用comparator接口实现
    public String PrintMinNumber1(int [] numbers) {
    	String res = "";
        if(numbers==null || numbers.length == 0){
          return res;
        }
		MString1 m[] = new MString1[numbers.length];
    	String st[] = Int2String(numbers);
    	int k=0;
    	for(String i:st){
    		m[k] = new MString1();
    		m[k++].s = i;
    	}
    	MString1Comparator m1c = new MString1Comparator();
    	Arrays.sort(m,m1c);
    	for (int i = 0; i < m.length; i++) {
    		res+=m[i].s;
		}
		return res;
    }
    
    class MString1{
    	public String s;
    }
    //方法二：无需修改要比较的类T。只需要写一个新的比较器类x，实现Comparator<T>接口，重写compareTo(T t1，T t2)方法。
    //然后Arrays.sort(T[],x)自动会对这个T[]数组采用x比较器方法，调用这个比较器。可实现复用。以后更改比较器方法方便了。
    class MString1Comparator implements Comparator<MString1>{
    	@Override
    	public int compare(MString1 o1, MString1 o2) {
    		String s1 = o1.s+o2.s;
    		String s2 = o2.s+o1.s;
    		if(s1.compareTo(s2) > 0){
    			return 1;
    		}else if(s1.compareTo(s2) <0)
    			return -1;
    		else return 0;
    	}
    }
   
    public static void main(String[] args) {
    	PrintMinNumberSolution pms = new PrintMinNumberSolution();
    	int a[] = new int []{3,32,321};
    	System.out.println("测试方法一：用comparable接口实现");
    	System.out.println(pms.PrintMinNumber(a));
    	System.out.println("测试方法二：用comparator接口实现");
    	System.out.println(pms.PrintMinNumber1(a));
    	
    	//测试数组两层new的区别。这也是为什么测试数组为空要两次，一个测引用为不为null，二个测具体的数组值为不为空
    	MString1[] mm;
    	mm = new MString1[4];
//    	mm[0] = new MString1();
    	int[] aa = new int[4];
    	aa[0] = 3;
    	String [] bb = new String[4];
    	bb[0] = "sg";
    	System.out.println(mm[0]+" "+aa[0]+" "+bb[0]);
    	
	}
}