import java.io.*;//前缀和:改题目要求 求一串整数数列中l~r中的数的和
//可以提前算好前n项的和s[n],然后用s[n] - s[n - 1]public class Main {static int n,m,l,r;static int N = 100010;static BufferedReader in = new BufferedReader(new InputStreamReader(System.in));static BufferedWriter out = new BufferedWriter(new OutputStreamWriter(System.out));static int[] g = new int[N];public static void main(String[] args) throws IOException {String[] init = in.readLine().split(" ");n = Integer.parseInt(init[0]);m = Integer.parseInt(init[1]);init = in.readLine().split(" ");for(int i = 1;i <= n;i ++) {g[i] = g[i - 1] + Integer.parseInt(init[i - 1]);}while(m-- > 0) {init = in.readLine().split(" ");l = Integer.parseInt(init[0]);r = Integer.parseInt(init[1]);out.write((g[r] - g[l - 1]) + "\n");}in.close();out.flush();}
}

前缀和例题:二维前缀和

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