[BOJ] 백준 1292 쉽게 푸는 문제

[문제]

https://www.acmicpc.net/problem/1292

 

 

[소스 코드]

import java.io.*;
import java.util.*;
public class Main {
    public static void main(String[] args) throws IOException {
    	BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    	StringTokenizer st = new StringTokenizer(br.readLine());
    	int a = Integer.parseInt(st.nextToken());
    	int b = Integer.parseInt(st.nextToken());
    	int result = func(b) - func(a-1);
    	System.out.println(result);
    }
    private static int func(int n) {
    	int result = 0;
    	int i = 1;
    	while(n>i) { 
    		result += i*i;
    		n -= i++;
    	}
    	return (result + n*i);
    }
}