java - 霍夫曼编码 - 符号分组

Question

我正在使用在互联网上找到的霍夫曼代码来获取以矩阵形式存储在二维数组中的随机整数的频率。

链接到霍夫曼代码 - Java:http://rosettacode.org/wiki/Huffman_coding

方法 Q1 要求用户设置矩阵大小。该矩阵填充有随机整数 [0, 255]。

public void q1(){
    System.out.println();
    System.out.println("Question 1 - Creating Random Matrix");

    Scanner in = new Scanner(System.in);

    //Matrix number of rows
    System.out.print("Insert size of rows M: ");
    rows = in.nextInt();

    //Matrix number of columns
    System.out.print("Insert size of columns N: ");
    columns = in.nextInt();

    System.out.println();

    matrix = new int[rows][columns];

    //Initialising randomisation
    Random r = new Random();

    //Filling matrix and printing values
    for (int m = 0; m < rows; m++){
        for (int n = 0; n < columns; n++){
            matrix[m][n] = r.nextInt(256);
            System.out.print("[" + matrix[m][n] + "] \t");
        }
        System.out.print("\n");
    }
    System.out.println();
}

方法Q2需要重新显示矩阵中找到的所有随机整数及其频率。

public void q2() {
    // we will assume that all our characters will have code less than 256, for simplicity
    int[] charFreqs = new int[256];
    StringBuilder sb = new StringBuilder();
    String [] st = new String[5];

    System.out.println();
    System.out.println("Alphabet " + "\t" + "Frequency" + "\t" + "Probability");
    for (int m = 0; m < rows; m++){
        for (int n = 0; n < columns; n++){
            String sentence = String.valueOf(matrix[m][n]);
            System.out.print(matrix[m][n] + "\n");

            //read each character and record the frequencies
            for (int i = 0; i < sentence.length(); i++){
                char c = sb.append(sentence[i]);
            }

            for (char c : sentence.toCharArray()){
                charFreqs[c]++;
            }
        }
    }       

    // build tree
    HuffmanTree tree = buildTree(charFreqs);

    // print out results
    System.out.println("SYMBOL\tWEIGHT\tHUFFMAN CODE");
    printCodes(tree, new StringBuffer());
}

当前程序通过将随机整数拆分为单独的数字来计算频率。我需要根据每个随机整数计算频率。

请问有什么帮助吗？

谢谢

Answer 1

使用 Java 8 流(如果可用)可以实现此目的的一种相当简单的方法:

Map<Integer, Integer> frequencies = Arrays.stream(matrix)
    .flatMap(Arrays::stream)
    .collect(Collectors.groupingBy(Function.identity(), Collectors.counting());