[Java][10828] 스택

문제:

https://www.acmicpc.net/problem/10828

10828번: 스택

코드:

import java.util.*;
import java.io.*;

public class Main {
	public static int MX = 10001;
	public static int [] dat = new int[MX];
	public static int pos = 0;
	
	public static void push(int x) { // 스택에 값 추가
		dat[pos++] = x;
	}
	public static void pop() { // 꼭대기 원소 제거
		if(pos != 0) {
			System.out.println(dat[pos-1]);
			dat[pos-1] = 0;
			pos--;
		}else {
			System.out.println(-1);
		}

	}
	public static void top() { // 꼭대기 값 학인
		if(pos != 0) {
			System.out.println(dat[pos-1]);
		}else{
			System.out.println(-1);
		}
	}
	public static int size() {
		int cnt = 0;
		for(int i=0;i<10001;i++) {
			if(dat[i] != 0) {
				cnt++;
			}
		}
		return cnt;
	}
	public static void empty() {
		if(dat[0] == 0) {
			System.out.println(1);
		}else {
			System.out.println(0);
		}
	}
    public static void main(String[] args) throws IOException { 
    	BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    	int n = Integer.parseInt(br.readLine());
    	StringBuilder sb = new StringBuilder();
    	
    	for(int i=0;i<n;i++) {
    		StringTokenizer st = new StringTokenizer(br.readLine());
			String commend = st.nextToken();
    		
    		if(commend.equals("push")) {
    			int val = Integer.parseInt(st.nextToken());
    			push(val);
    		}
    		if(commend.equals("pop")) {
    			pop();
    		}
    		if(commend.equals("size")) {
    			System.out.println(size());
    		}
    		if(commend.equals("empty")) {
    			empty();
    		}
    		if(commend.equals("top")) {
    			top();
    		}
    	}
    }	
}

위 직접 구현

아래 코드 참고 구현

import java.util.*;
import java.io.*;

public class Main {
	public static int MX = 10001;
	public static int [] dat = new int[MX];
	public static int pos = 0;
	
	public static void push(int x) { // 스택에 값 추가
		dat[pos++] = x;
	}
	public static void pop() { // 꼭대기 원소 제거
		pos--;
	}

	public static int top() { // 꼭대기 값 학인
		return dat[pos-1];
	}
    public static void main(String[] args) throws IOException { 
    	BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    	int n = Integer.parseInt(br.readLine());
    	StringBuilder sb = new StringBuilder();
    	
    	for(int i=0;i<n;i++) {
    		StringTokenizer st = new StringTokenizer(br.readLine());
			String commend = st.nextToken();
			
    		switch(commend) {
    		case "push" :
    			int val = Integer.parseInt(st.nextToken());
    			push(val);
    			break;
    		case "pop" :
    			if(pos == 0) {
    				System.out.println(-1);
    			}else {
    				System.out.println(top());
    				pop();
    			}
    			break;
    		case "size" :
    			System.out.println(pos);
    			break;
    		case "empty" :
    			if(pos == 0) {
    				System.out.println(1);
    			}else {
    				System.out.println(0);
    			}
    			break;
    		case "top" :
    			if(pos == 0) {
    				System.out.println(-1);
    			}else {
    				System.out.println(top());
    			}
    			break;
    		}
    		
    		/*
    		if(commend.equals("push")) {
    			int val = sc.nextInt();
    			push(val);
    		}
    		if(commend.equals("pop")) {
    			if(pos == 0) {
    				System.out.println(-1);
    			}else {
    				System.out.println(top());
    				pop();
    			}
    		}
    		if(commend.equals("size")) {
    			System.out.println(pos);
    		}
    		if(commend.equals("empty")) {
    			if(pos == 0) {
    				System.out.println(1);
    			}else {
    				System.out.println(0);
    			}
    		}
    		if(commend.equals("top")) {
    			if(pos == 0) {
    				System.out.println(-1);
    			}else {
    				System.out.println(top());
    			}
    		}*/
    	}
    }	
}

 

scanner 대신 쓸 buffer에 관한 공부 필요

 

참고

https://github.com/encrypted-def/basic-algo-lecture/blob/master/0x05/solutions/10828.cpp

GitHub - encrypted-def/basic-algo-lecture: 바킹독의 실전 알고리즘 강의 자료