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言語処理100本ノック 第1章: 準備運動 06

06. 集合

"paraparaparadise"と"paragraph"に含まれる文字bi-gramの集合を,それぞれ, XとYとして求め,XとYの和集合,積集合,差集合を求めよ.さらに,'se'というbi-gramがXおよびYに含まれるかどうかを調べよ.

java

package net.vg4;

import java.util.*;

class NGram {
    public List<List<String>> make(List<String> list, int n) {
        ArrayList<List<String>> alistlist = new ArrayList<>();
        for (int from = 0; from < list.size(); from++) {
            int to = from + n;
            if (to > list.size()) {
                to = list.size();
            }
            List<String> listr = list.subList(from, to);
            alistlist.add(listr);
        }
        return alistlist;
    }

    public List<List<String>> make(String str, int n) {
        return this.make(Arrays.asList(str.split("")), n);
    }
}

public class Main {
    public static void main(String[] args) {
        String sample1 = "paraparaparadise";
        String sample2 = "paragraph";

        NGram ngram = new NGram();

        List<List<String>> res1 = ngram.make(sample1, 2);
        Set<List<String>> xOrg = new HashSet<>(res1);

        List<List<String>> res2 = ngram.make(sample2, 2);
        Set<List<String>> y = new HashSet<>(res2);

        // 和集合
        {
            List<List<String>> x = new ArrayList<List<String>>(xOrg);
            x.addAll(y);
            System.out.println(x);
        }

        // 積集合
        {
            List<List<String>> x = new ArrayList<List<String>>(xOrg);
            x.retainAll(y);
            System.out.println(x);
        }

        // 差集合
        {
            List<List<String>> x = new ArrayList<List<String>>(xOrg);
            x.removeAll(y);
            System.out.println(x);
        }

        List<String> seed = Arrays.asList("s", "e");

        if (xOrg.contains(seed)) {
            System.out.println("including in x");
        }
        if (y.contains(seed)) {
            System.out.println("including in y");
        }

    }
}