問題描述

您好，我有一個 HashMap<String, Double> 以及一個返回雙精度值的函數，稱為 answer.我想檢查 HashMap 中的哪個值最接近答案，然后獲取該值的鍵并打印它.

Hi I have a HashMap<String, Double> and also a function which returns a double value known as answer. I want to check which value in the HashMap is the closest to the answer and then grab that value's key and print it.

HashMap<String, Double> output = new HashMap<String, Double>();


contents
("A", 0)
("B", 0.25)
("C", 0.5)
("D", 0.75)
("E", 1)

假設我的一個函數的答案是 0.42，我如何檢查它最接近哪個值，然后獲取該值的鍵.我無法切換 HashMap 的鍵和值(因為之前的函數將值平均分配給每個字母)，否則最好遍歷每個鍵并獲取值.

Suppose the answer to one of my functions was 0.42, how can I check which value it is closest to and then grab the key to that value. I cant switch around the key and value of the HashMap (as a previous function assigns the values equally to each letter), otherwise it would be better to go through each key and get the value.

推薦答案

如果你的值是唯一的，你可以使用 TreeMap，實現 NavigableMap，它有很好的 ceilingKey 和 floorKey 方法:

If your values are unique, you can use a TreeMap, which implements NavigableMap, which has the nice ceilingKey and floorKey methods:

    NavigableMap<Double, String> map = new TreeMap<>();
    map.put(0d, "A");
    map.put(0.25, "B");
    map.put(0.5, "C");
    map.put(0.75, "D");
    map.put(1d, "E");

    double value = 0.42;
    double above = map.ceilingKey(value);
    double below = map.floorKey(value);

    System.out.println(value - below > above - value ? above : below); //prints 0.5

注意:如果 value 小于(或大于)最小/最大鍵，則兩種方法都可以返回 null.

Note: both methods can return null if value is less (resp. greater) than the smallest / largest key.

這篇關于Java - 如何從最接近特定數字的哈希圖中找到一個值?的文章就介紹到這了，希望我們推薦的答案對大家有所幫助，也希望大家多多支持html5模板網！