算法题：5万条URL，如何按照出现次数快速排序

题目：5万条URL，统计出现的次数，并进行排序

解题思路：使用散列表来映射URL，统计每个URL出现的次数，然后再进行排序。

/**
 * 5w URL统计出现的次数，并进行排序
 */
public class URLCountSort {

    public static void main(String[] args) {
        int limit = 50000;
        int[] array1 = new Random().ints(limit, 1, 10000).toArray();
        String[] array2 = new String[limit];
        for(int i=0; i<limit; i++) {
            array2[i] = "www.itzhimei.com/"+array1[i];
        }

        Map<String, Integer> urlMap = new HashMap<>();
        Arrays.stream(array2).forEach(x->{
            if(urlMap.containsKey(x)) {
                urlMap.put(x,urlMap.get(x)+1);
            } else {
                urlMap.put(x,1);
            }
        });

        System.out.println(urlMap.size());
        List<Map.Entry<String, Integer>> collect = urlMap.entrySet().stream()
                .sorted((e1, e2) -> e2.getValue().compareTo(e1.getValue()))
                .collect(Collectors.toList());

        collect.stream().limit(10).forEach(x-> System.out.println(x.getKey() + ":" + x.getValue()));

    }
}

输出打印出现最多的10条URL：

www.itzhimei.com/3091:15
www.itzhimei.com/1307:14
www.itzhimei.com/2043:14
www.itzhimei.com/8351:14
www.itzhimei.com/1609:13
www.itzhimei.com/7107:13
www.itzhimei.com/1002:13
www.itzhimei.com/869:13
www.itzhimei.com/4568:13
www.itzhimei.com/4547:13