[백준 8일차 / 하루 3문제] 8393번, 25304번, 15552번

1. 8393번

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.IOException;
 
public class Main {
	public static void main(String[] args) throws IOException {
        
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
 
		int N = Integer.parseInt(br.readLine());
		br.close();
		int s = 0;
 
		for( int i = 1 ; i <= N ; i++ ) s+=i;
 
		System.out.println(s);
	}
}

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2. 25304번 영수증

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

public class Main {
    public static void main(String[] args) throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        StringTokenizer st;

        int X = Integer.parseInt(br.readLine());
        int N = Integer.parseInt(br.readLine());

        int total = 0;
        for(int i = 0; i < N; i++) {
            st = new StringTokenizer(br.readLine());
            total += Integer.parseInt(st.nextToken()) * Integer.parseInt(st.nextToken());
        }
        if(X == total) System.out.println("Yes");
        else System.out.println("No");
    }
}

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3. 15552번 빠른 A+B

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.util.StringTokenizer;
 
public class Main {
 
	public static void main(String[] args) throws IOException {
 
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));
 
 
		int N = Integer.parseInt(br.readLine());
        
		StringTokenizer st;
 
		for (int i = 0; i < N; i++) {
			st = new StringTokenizer(br.readLine()," ");
			bw.write((Integer.parseInt(st.nextToken()) + Integer.parseInt(st.nextToken()))+ "\n");
		}
		br.close();
        
		bw.flush();
		bw.close();
 
	}
}