题解 | 【模板】静态区间和（前缀和）

package main

import (
	"bufio"
	"fmt"
	"os"
)

type FastScanner struct {
	r *bufio.Reader
}

func NewFastScanner() *FastScanner {
	return &FastScanner{r: bufio.NewReaderSize(os.Stdin, 1<<20)}
}

func (fs *FastScanner) NextInt() int {
	sign, val := 1, 0
	c, _ := fs.r.ReadByte()
	for (c < '0' || c > '9') && c != '-' {
		c, _ = fs.r.ReadByte()
	}
	if c == '-' {
		sign = -1
		c, _ = fs.r.ReadByte()
	}
	for c >= '0' && c <= '9' {
		val = val*10 + int(c-'0')
		c, _ = fs.r.ReadByte()
	}
	fs.r.UnreadByte()
	return sign * val
}

func main() {
	in := NewFastScanner()
	out := bufio.NewWriterSize(os.Stdout, 1<<20)
	defer out.Flush()

	n := in.NextInt()
	q := in.NextInt()

	prefix := make([]int64, n+1)
	for i := 1; i <= n; i++ {
		x := int64(in.NextInt())
		prefix[i] = prefix[i-1] + x
	}

	for i := 0; i < q; i++ {
		l := in.NextInt()
		r := in.NextInt()
		fmt.Fprintln(out, prefix[r]-prefix[l-1])
	}
}