将 HashMap 存储在另一个 HashMap 中并提高性能

问题描述

我应该在另一个 HashMap 中创建一个 HashMap 如下所示，它可以根据键将值存储在内部 HashMap 中运行时外层HashMap

I am supposed to created a HashMap inside another HashMap as shown below which can store the value inside the inner HashMap based on the key of the outer HashMap at the runtime

即程序所需的输出应该是格式

i.e. required output for program should be of the format

   { 1 = {11 = "aaa",15 = "bbb"}, 2 = {13 = "ccc", 14 = "ddd"} }

其中 1,2 是 Outer HashMap 的键值.

where 1,2 are Key values for Outer HashMap.

下面是为其提供的代码有没有更好的方法来提高性能

Below is the Code provided for it Is there any better approach to improve performance

HashMap<Integer, HashMap<Integer, String>>Outer 
                   = new HashMap<Integer, HashMap<Integer,String>>();

    BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    int count = Integer.parseInt(br.readLine());
    for(int i =0;i<count;i++)
    {
        String input[] = br.readLine().split("\s");

        //HashMap<Integer,String>inner = new HashMap<Integer, String>();
        int key = Integer.parseInt(input[0]);
        if(Outer.isEmpty() || !Outer.containsKey(key))
        {
            HashMap<Integer, String> inner = new HashMap<Integer, String>();
            inner.put(Integer.parseInt(input[1]),input[2]);
            Outer.put(key, inner);
        }
        else if(Outer.containsKey(key))
            {
                HashMap<Integer, String> inner = (HashMap<Integer, String>) Outer.get(key).clone();
                inner.put(Integer.parseInt(input[1]), input[2]);
                Outer.put(key, inner);
            }
    }

推荐答案

类似于 Vadim 的答案，但进一步改进 - 因为它不需要同时调用 containsKey 和 获取:

Similar to Vadim's answer, but further improved - as it doesn't require a call to both containsKey as well as get:

Map<Integer, Map<Integer, String>> outer = new HashMap<Integer, Map<Integer, String>>();
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
int count = Integer.parseInt(br.readLine());

Pattern splitter = Pattern.compile("\s");

for(int i = 0; i < count; i++){
    String input[] = splitter.split(br.readLine());

    int key = Integer.parseInt(input[0]);

    Map<Integer, String> inner = outer.get(key);
    if(inner == null){
        inner = new HashMap<Integer, String>();
        outer.put(key, inner);
    }
    inner.put(Integer.parseInt(input[1]), input[2]);
}

它还对命名约定以及使用 Collections 接口而不是具体类型进行了一些小的改进.

It also has some minor improvements for naming conventions, and use of the Collections interfaces instead of concrete types.

我还删除了对 clone 的调用.这可能会节省一点点 - 我认为它不会给您带来预期的结果.

I also removed the call to clone. This could be a slight savings - and I don't think it would have given you your expected results.

最后 - 我更改的另一件事可能会略有改进，即使用预编译模式将字符串拆分为字段.

Finally - one other thing that I changed that could be a slight improvement is using a pre-compiled Pattern for the splitting of your String into fields.

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