[백준] 17390 이건 꼭 풀어야 해!

정렬해서 누적합을 빼주면 되는 문제
선택정렬, 버블정렬 정도는 복습하자..

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.Arrays;
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 = new StringTokenizer(br.readLine(), " ");
        int N = Integer.parseInt(st.nextToken());
        int Q = Integer.parseInt(st.nextToken());

        st = new StringTokenizer(br.readLine(), " ");
        int[] arr = new int[N];
        int[] sum = new int[N+1];
        for(int i = 0; i < N; i++) {
            arr[i] = Integer.parseInt(st.nextToken());
        }

        Arrays.sort(arr);

        for(int i = 1; i <= N; i++) {
            sum[i] = sum[i-1] + arr[i-1];
        }

        for(int i = 0; i < Q; i++) {
            st = new StringTokenizer(br.readLine(), " ");
            int L = Integer.parseInt(st.nextToken());
            int R = Integer.parseInt(st.nextToken());

            System.out.println(sum[R] - sum[L-1]);
        }
    }
}