java-68-把数组排成最小的数。一个正整数数组，将它们连接起来排成一个数，输出能排出的所有数字中最小的。例如输入数组{32, 321}，则输出32132
import java.util.Arrays;import java.util.Comparator;public class MinNumFromIntArray {/** * Q68输入一个正整数数组，将它们连接起来排成一个数，输出能排出的所有数字中最小的一个。 * 例如输入数组{32, 321}，则输出这两个能排成的最小数字32132。请给出解决问题的算法，并证明该算法。 */public static void main(String[] args) {int[][] val={{32,321},//32132{532,45,78},//4553278{2,23,231},//223123{2,3,1},//123};for(int[] x:val){//solution 1String result=minNumFromIntArray(x);System.out.println(result);//solution 2AuxClass minStr=new AuxClass();minNumFromIntArray2(x,0,x.length-1,minStr);System.out.println(minStr.str);}//System.out.println("32".compareTo("321"));//<0}/*solution 1: * if ab<ba,then a<b * 1.sort the integer array. the comparator is "if ab<ba,then a<b" * 2.append each integer in the array to create a string and that's the result. */public static String minNumFromIntArray(int[] x){String[] strs=stringsOf(x);Arrays.sort(strs,new Comparator<String>(){public int compare(String o1, String o2) {return (o1+o2).compareTo(o2+o1);}});StringBuilder sb=new StringBuilder();for(String each:strs){sb.append(each);}return sb.toString();}//int[] to String[].For comparing.public static String[] stringsOf(int[] x){int len=x.length;String[] strs=new String[len];for(int i=0;i<len;i++){strs[i]=""+x[i];}return strs;}/*solution 2 * get all the permutations. * find the min. * Of course we use String instead of Big Integer. */public static void minNumFromIntArray2(int[] x,int first,int last,AuxClass minStr){if(first==last){StringBuilder sb=new StringBuilder();for(int each:x){sb.append(each);}if(minStr.str==null){minStr.str=sb.toString();}else{if(minStr.str.compareTo(sb.toString())>0){minStr.str=sb.toString();}}return;}for(int i=first;i<=last;i++){swap(x,first,i);minNumFromIntArray2(x,first+1,last,minStr);swap(x,first,i);}}public static void swap(int[] x,int i,int j){int temp=x[i];x[i]=x[j];x[j]=temp;}/* * when you use 'String' instead of inner class,you get 'null' all the time */static class AuxClass{String str;}}