题目：输入一个正整数数组，把数组里所有数字拼接起来排成一个数，打印能拼接出的所有数字中最小的一个。

代码如下：

package demo;

import java.util.Comparator;

/**
 * 把数组排成最小的数
 * 
 * @author xiangdonglee
 *
 */
public class Test33 {
    /**
     * 自定义的排序比较器，实现算法说明的排序原理
     * 
     * @author xiangdonglee
     *
     */
    private static class MComparator implements Comparator<String> {
        @Override
        public int compare(String o1, String o2) {
            if (o1 == null || o2 == null) {
                throw new IllegalArgumentException("Arg should not be null!");
            }
            String s1 = o1 + o2;
            String s2 = o2 + o1;
            return s1.compareTo(s2);
        }
    }

    /**
     * 快速排序算法
     * 
     * @param array
     *            待排序数组
     * @param start
     *            要排序的起始位置
     * @param end
     *            要排序的结束位置
     * @param comparator
     *            自定义的比较器
     */
    private static void quickSort(String[] array, int start, int end, Comparator<String> comparator) {
        if (start < end) {
            // pivot：枢轴、中心点
            String pivot = array[start];
            int left = start;
            int right = end;
            while (start < end) {
                while (start < end && comparator.compare(array[end], pivot) >= 0) {
                    end--;
                }
                array[start] = array[end];
                while (start < end && comparator.compare(array[start], pivot) <= 0) {
                    start++;
                }
                array[end] = array[start];
            }
            array[start] = pivot;
            quickSort(array, left, start - 1, comparator);
            quickSort(array, start + 1, end, comparator);
        }
    }

    /**
     * 
     * @param array
     *            输入的数组
     * @return 输出结果
     */
    public static String printMinNumber(String[] array) {
        if (array == null || array.length < 1) {
            throw new IllegalArgumentException("Array must contain value!");
        }
        MComparator comparator = new MComparator();
        quickSort(array, 0, array.length - 1, comparator);
        StringBuilder builder = new StringBuilder(256);
        for (String s : array) {
            builder.append(s);
        }
        return builder.toString();
    }

    public static void main(String[] args) {
        String[] data1 = { "3", "5", "1", "4", "2" };
        System.out.println(printMinNumber(data1));
        String[] data2 = { "3", "32", "321" };
        System.out.println(printMinNumber(data2));
        String[] data3 = { "3", "323", "32123" };
        System.out.println(printMinNumber(data3));
        String[] data4 = { "1", "11", "111" };
        System.out.println(printMinNumber(data4));
        String[] data5 = { "321" };
        System.out.println(printMinNumber(data5));
    }
}

运行结果

来源：http://blog.csdn.net/derrantcm/article/details/46753221