[자료구조] List, Map, Set, Stack, Queue 연습 (JAVA)

기본적인 자료구조 다루기 연습

(Collections 를 사용한 sort)

 

 

import java.util.List;
import java.util.Map;
import java.util.HashMap;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Stack;
import java.util.Queue;
import java.util.LinkedList;
import java.util.PriorityQueue;
import java.util.HashSet;
import java.util.TreeSet;
import java.util.Iterator;
 
public class Main {
 
    public static void main(String[] args) {
        
        // List
        List <Integer> list  = new ArrayList<Integer>();
        list.add(1);
        list.add(2);
        list.add(3);
        list.remove(2);
        
        for(int i=0 ;i < list.size(); i++)
            System.out.print(list.get(i)+" "); //1 2
        
        // HashMap 
        HashMap <Integer, String> map = new HashMap<>();
        map.put(26, "AAA");
        map.put(28, "CCC");
        map.put(29, "BBB");
        System.out.println("\n"+ map.getOrDefault(30, "NO")); //NO
        
        for(Map.Entry<Integer, String> entry: map.entrySet()) {
            System.out.println(entry.getKey() +" " + entry.getValue()); 
        }
        // 26 AAA
        // 28 CCC
        // 29 BBB
        
        List<Integer> keylist = new ArrayList<>(map.keySet());
        List<String> vallist = new ArrayList<>(map.values());
        
        System.out.println(keylist); //26 28 29
        System.out.println(vallist); //AAA CCC BBB
        
        System.out.println(keylist.contains(25)); //false
        
        //sort, max, min
        System.out.println(Collections.max(keylist)); //29
        System.out.println(Collections.min(vallist)); //AAA
        
        Collections.sort(vallist); 
        System.out.println(vallist); //AAA BBB CCC
        
        
        //Stack
        Stack <Integer> stack = new Stack<>();
        stack.push(1);
        stack.push(5);
        stack.push(3);
        
        System.out.println(stack); //1, 5, 3
        System.out.println(stack.peek()); //3
        
        stack.pop();
        System.out.println(stack.pop()); //5
        System.out.println(stack); //1
        
        for(int i=0; i< stack.size(); i++) {
            System.out.println(stack.get(i));
        }
        //1
        
        //Queue
        Queue<Integer> queue = new LinkedList<>();
        queue.add(1);
        queue.add(5);
        queue.add(3);
        System.out.println(queue);  //1, 5, 3
        
        System.out.println(queue.remove()); //1
        System.out.println(queue.remove()); //5
        
        //PriorityQueue
        PriorityQueue<Integer> pq = new PriorityQueue<>(); //우선순위 : 낮은 숫자 순
        pq.add(30);
        pq.add(50);
        pq.add(10);
        pq.add(20);
        
        pq.remove(); //10 제거
        System.out.println(pq.peek()); //20
        System.out.println(pq.remove()); //20
        System.out.println(pq.remove()); //30
        System.out.println(pq.remove()); //50
        
        //PriorityQueue<Integer> rpq = new PriorityQueue<>(Collections.reverseOrder()); //우선순위 : 높은 숫자 순
        
        
        //HashSet
        HashSet<Integer> set = new HashSet<>();
        set.add(3);
        set.add(4);
        set.add(1);
        set.add(5);
        set.add(2);
        
        Iterator<Integer> it = set.iterator();
        while(it.hasNext()) {
            System.out.print(it.next()+" "); //순서없으므로 있는 원소 전부 출력
        }
        System.out.println();
        
        //hash set 정렬
        List<Integer> setsort = new ArrayList<>(set);
        Collections.sort(setsort); 
        System.out.println(setsort); // 1 2 3 4 5
        Collections.reverse(setsort); //내림차순 정렬
        System.out.println(setsort); // 5 4 3 2 1
        
        System.out.println(setsort.contains(3)); //true
        
        TreeSet<Integer> ts = new TreeSet<>(); //오름차순
        ts.add(3);
        ts.add(2);
        ts.add(10);
        ts.add(7);
        for(Integer i:ts) {
            System.out.print(i+" "); //2 3 7 10
        }
        System.out.println();
        
        
        
    }
 
}