题解 | #【模板】前缀和#

// 注意类名必须为 Main, 不要有任何 package xxx 信息
public class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        // 注意 hasNext 和 hasNextLine 的区别
        while (in.hasNextInt()) { // 注意 while 处理多个 case
            int n = in.nextInt();
            int q = in.nextInt();
            int[] arr = new int[n];
            for (int i = 0; i < n; i++) {
                arr[i] = in.nextInt();
            }
            long[] dp = genDp(arr);
            for (int i = 0; i < q; i++) {
                int l = in.nextInt();
                int r = in.nextInt();
                long sum = l < 2 ? dp[r - 1] : dp[r - 1] - dp[l - 2];
                System.out.println(sum);
            }
            
        }
    }
    
    public static long[] genDp(int[] arr) {
        if (arr == null || arr.length < 1) {
            return new long[0];
        }
        int n = arr.length;
        long[] dp = new long[n];
        // dp[0]
        dp[0] = arr[0];
        for (int i = 1; i < n; i++) {
            dp[i] = dp[i - 1] + arr[i];
        }
        return dp;
    }
}