tenid's dev

1. 문제 설명

#include <string>
#include <vector>
#include <map>

using namespace std;

vector<int> solution(vector<string> name, vector<int> yearning, vector<vector<string>> photo) {
    vector<int> answer;

    map<string, int> person_map;

    for (int i =0 ; i < yearning.size() ; i++)
    {
        person_map[name[i]] = yearning[i];

    }


    for (int j = 0; j < photo.size(); j++)
    {
        int sum = 0;

        for (int k = 0; k < photo[j].size(); k++)
        {

            sum += person_map[photo[j][k]];


        }

        answer.push_back(sum);
    }





    return answer;
}

1. 문제 설명

#include <string>
#include <vector>
#include <map>

using namespace std;

vector<string> solution(vector<string> players, vector<string> callings) {
    map<string, int> player_map;


    for (int i = 0; i < players.size(); i++)
    {
        player_map[players[i]] = i;

    }



    for (string call : callings)
    {
        string currentPlayer = call;
        string prePlayer = players[player_map[call] - 1];

        // 스왑
        swap(players[player_map[currentPlayer]], players[player_map[prePlayer]]);
        
        // map 순위 반영
        player_map[currentPlayer]--;
        player_map[prePlayer]++;


    }



    return players;
}

#include <iostream>

using namespace std;

class Queue {
private:
	int arr[10000];
	int head;
	int tail;

public:

	void init() {
		head = -1;
		tail = -1;
	}


	void push(int data) {

		if (head == -1)
			head++;

		arr[++tail] = data;

	}

	int size() {
		if (tail < 0)
			return 0;

		return tail - head + 1;

	}


	bool empty() {
		return  size() <= 0;
	}

	int pop() {
		if (empty())
			return -1;

		return arr[head++];
	}

	int front()
	{
		if (empty())
			return -1;

		return arr[head];
	}


	int back()
	{
		if (empty())
			return -1;


		return arr[tail];
	}



};

int main()
{

	int N;
	cin >> N;

	Queue q;
	q.init();

	string command;

	for (int i = 0; i < N; i++)
	{
		cin >> command;

		if (command == "push")
		{
			int data;
			cin >> data;
			q.push(data);

		}
		else if (command == "pop")
		{
			cout << q.pop() << endl;;
		}
		else if (command == "size")
		{
			cout << q.size() << endl;
		}
		else if (command == "empty")
		{
			cout << q.empty() << endl;
		}
		else if (command == "front")
		{
			cout << q.front() << endl;
		}
		else if (command == "back")
		{
			cout << q.back() << endl;
		}
		

	}




}

여러 가지 구현 방법이 있지만 스택 개념에서 확장하여 입구가 2개(앞,뒤)로 생각하여 구현 해봤다.

출처 : https://www.acmicpc.net/problem/10845

#include <iostream>
#include <string>


using namespace std;

class stack {

private:
	int arr[10000];
	int cursor;

public:
	void init() {
		cursor = -1;
	}

	void push(int data) {
		arr[++cursor] = data;
	}

	bool empty() {
		return cursor < 0;
	}

	int pop() {
		if (empty())
			return -1;


		return arr[cursor--];
	}

	int size() {
		return cursor + 1;
	}

	int top() {
		
		if (empty()) {
			return -1;
		}

		return arr[cursor];
	}


};



int main()
{
	int N;
	cin >> N;

	stack s;
	s.init();

	string command;

	for (int i = 0; i < N; i++)
	{
		cin >> command;

		if (command == "push")
		{
			int data;
			cin >> data;
			s.push(data);

		}
		else if (command == "top")
		{
			cout << s.top() << endl;;
		}
		else if (command == "size")
		{
			cout << s.size() << endl;
		}
		else if (command == "empty")
		{
			cout << s.empty() << endl;
		}
		else if (command == "pop")
		{
			cout << s.pop() << endl;;
		}

	}


}

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

1. 문제 설명

괄호가 바르게 짝지어졌다는 것은 '(' 문자로 열렸으면 반드시 짝지어서 ')' 문자로 닫혀야 한다는 뜻입니다. 예를 들어

"()()" 또는 "(())()" 는 올바른 괄호입니다.
")()(" 또는 "(()(" 는 올바르지 않은 괄호입니다.
'(' 또는 ')' 로만 이루어진 문자열 s가 주어졌을 때, 문자열 s가 올바른 괄호이면 true를 return 하고, 올바르지 않은 괄호이면 false를 return 하는 solution 함수를 완성해 주세요.

- 제한 사항

• 문자열 s의 길이 : 100,000 이하의 자연수
• 문자열 s는 '(' 또는 ')' 로만 이루어져 있습니다.

2. 풀이 코드

#include <string>
#include <iostream>

using namespace std;

bool solution(string s)
{
    int cnt = 0;
    for(char c : s)
      {
        if(c == '(')
          cnt++;
        else if(c == ')')
          cnt--;

        if(cnt<0)
          return false;
      }
    return cnt==0;
}

3. 정리

문자열 전체를 순회 하면서 괄호의 짝이 맞는지를 체크하는 것이 관건인 문제이다. 따라서 '(' 일때는 +1를 하고 ')' -1를 하며 기본적으로 마지막에 0이 되면 올바른 괄호로 판단하지만 순회하는 중간 카운트가 0보다 작으면 올바르지 않은 ')'가 나온 것이므로 바로 false를 리턴한다.

전체 시간 복잡도는 문자열 길이만큼 순회하기 때문에 O(N) 이다.

출처 :https://school.programmers.co.kr/learn/courses/30/lessons/12909

Exception 처리

Web Application 의 입장에서 바라 보았을 때, 에러가 났을 때 내려줄 수 있는 방법은 많지 않다.

1. 에러 페이지
2. 4XX Error or 5XX Error
3. Client가 200 외에 처리를 하지 못 할 때는 200을 내려주고 별도의 에러 Message 전달

Web Application 입장에서는 이런 에러는 try-catch로 그 때 마다 묶는 것이 아닌 한 곳에 모아서 처리하는게 제일 편리하다.

package com.example.exception.advice;

import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.MethodArgumentNotValidException;
import org.springframework.web.bind.annotation.ExceptionHandler;
import org.springframework.web.bind.annotation.RestControllerAdvice;

@RestControllerAdvice
public class GlobalControllerAdvice {

    @ExceptionHandler(value = Exception.class)
    public ResponseEntity exception(Exception e) {
        System.out.println(e.getClass().getName());

        return ResponseEntity.status(HttpStatus.INTERNAL_SERVER_ERROR).body("");
    }

    @ExceptionHandler(value = MethodArgumentNotValidException.class)
    public ResponseEntity methodArgumentNotValidException(MethodArgumentNotValidException e) {

        return ResponseEntity.status(HttpStatus.BAD_REQUEST).body(e.getMessage());
    }

}

@RestControllerAdvice 어노테이션을 설정 함으로써 Spring Web Application 안의 Exception 들을 Global하게 처리할 수 있다.  basePackages 값을 넣으면 원하는 패키지도 설정이 가능하다.

@ExceptionHandler 를 이용하여 특정 Exception에 대해 어떤 처리를 할 지 메소드를 정의할 수 있다.

package com.example.exception.controller;

import com.example.exception.dto.User;
import jakarta.validation.Valid;
import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.MethodArgumentNotValidException;
import org.springframework.web.bind.annotation.*;

@RestController
@RequestMapping("/api")
public class ApiController {
    @PostMapping("/post")
    public User post(@Valid @RequestBody User user) {
        return user;
    }

    @ExceptionHandler(value = MethodArgumentNotValidException.class)
    public ResponseEntity methodArgumentNotValidException(MethodArgumentNotValidException e) {

        return ResponseEntity.status(HttpStatus.BAD_REQUEST).body(e.getMessage());
    }

}

컨트롤러 내부에  @ExceptionHandler가 정의되어 있는 경우 @RestControllerAdvice, @ControllerAdvice 등 보다 우선순위가 높아 컨트롤러 개별 Exception 처리를 할 수 있다.

추가 예제 (Validation & Exception)

package com.example.exception.controller;

import com.example.exception.dto.User;
import jakarta.validation.Valid;
import jakarta.validation.constraints.Min;
import jakarta.validation.constraints.NotNull;
import jakarta.validation.constraints.Size;
import org.springframework.validation.annotation.Validated;
import org.springframework.web.bind.annotation.*;

@RestController
@RequestMapping("/api")
@Validated
public class ApiController 

    @GetMapping("/get")
    public User get(
            @NotNull
            @Size(min=2)
            @RequestParam String name,

            @NotNull
            @Min(1)
            @RequestParam Integer age) {

        User user = new User();
        user.setName(name);
        user.setAge(age);

        int a = 10+age;

        return user;
    }


    @PostMapping("/post")
    public User post(@Valid @RequestBody User user) {
        return user;
    }

}

@Validated은 스프링에서 제공하는 어노테이션으로써 컨트롤러뿐만 아니라 서비스, 레포지토리 등 모든 계층의 그룹 기반 유효성 검증을 지원한다. 예외로 ConstraintViolationException 발생한다.

package com.example.exception.dto;

public class Error {
    private String field;
    private String message;
    private String invalidValue;

   // get/set , toString 메소드 생략

}

package com.example.exception.dto;

import java.util.List;

public class ErrorResponse {

    String statusCode;
    String requestUrl;
    String code;
    String message;
    String resultCode;

    List<Error> errorList;

 // get/set , toString 메소드 생략
 
}

package com.example.exception.advice;

import com.example.exception.controller.ApiController;
import com.example.exception.dto.Error;
import com.example.exception.dto.ErrorResponse;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.validation.ConstraintViolationException;
import jakarta.validation.ElementKind;
import jakarta.validation.Path;
import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.validation.BindingResult;
import org.springframework.validation.FieldError;
import org.springframework.web.bind.MethodArgumentNotValidException;
import org.springframework.web.bind.MissingServletRequestParameterException;
import org.springframework.web.bind.annotation.ExceptionHandler;
import org.springframework.web.bind.annotation.RestControllerAdvice;

import java.util.ArrayList;
import java.util.List;

@RestControllerAdvice(basePackageClasses = ApiController.class)
public class ApiControllerAdvice {


    @ExceptionHandler(value = MissingServletRequestParameterException.class)
    public ResponseEntity missingServletRequestParameterException(MissingServletRequestParameterException e, HttpServletRequest request) {
        List<Error> errorList = new ArrayList<>();

        String fieldName = e.getParameterName();
        String invalidValue = e.getMessage();

        Error errorElement = new Error();
        errorElement.setField(fieldName);
        errorElement.setMessage(invalidValue);
        errorList.add(errorElement);

        ErrorResponse errorResponse = new ErrorResponse();
        errorResponse.setErrorList(errorList);
        errorResponse.setMessage("missingServletRequestParameterException");
        errorResponse.setRequestUrl(request.getRequestURI());
        errorResponse.setStatusCode(HttpStatus.BAD_REQUEST.toString());
        errorResponse.setResultCode("FAILED");


        return ResponseEntity.status(HttpStatus.BAD_REQUEST).body(errorResponse);
    }



}

컨트롤러에서 validation 단계에서 exception이 발생한 경우 위와 같이 클라이언트의 잘못된 요청에 대하여 원하는 응답을 내려줄 수 있다.

{
    "statusCode": "400 BAD_REQUEST",
    "requestUrl": "/api/get",
    "code": null,
    "message": "constraintViolationException",
    "resultCode": "FAILED",
    "errorList": [
        {
            "field": "age",
            "message": "1 이상이어야 합니다",
            "invalidValue": "0"
        }
    ]
}