Problem:
Score : 600 points

Problem Statement

We have N colored balls arranged in a row from left to right; the color of the i-th ball from the left is c_i.

You are given Q queries. The i-th query is as follows: how many different colors do the l_i-th through r_i-th balls from the left have?

Constraints

1\leq N,Q \leq 5 \times 10^5

1\leq c_i \leq N

1\leq l_i \leq r_i \leq N

All values in input are integers.

Input

Input is given from Standard Input in the following format:

N Q
c_1 c_2 \cdots c_N
l_1 r_1
l_2 r_2
:
l_Q r_Q

Output

Print Q lines. The i-th line should contain the response to the i-th query.

Sample Input 1

4 3
1 2 1 3
1 3
2 4
3 3

Sample Output 1

2
3
1

The 1-st, 2-nd, and 3-rd balls from the left have the colors 1, 2, and 1 - two different colors.

The 2-st, 3-rd, and 4-th balls from the left have the colors 2, 1, and 3 - three different colors.

The 3-rd ball from the left has the color 1 - just one color.

Sample Input 2

10 10
2 5 6 5 2 1 7 9 7 2
5 5
2 4
6 7
2 2
7 8
7 9
1 8
6 9
8 10
6 8

Sample Output 2

1
2
2
1
2
2
6
3
3
3

Solution in Go (1.14.1) (judge verdict: Time Limit Exceeded)

package main

import (
	"bufio"
	"fmt"
	"os"
	"sort"
	"strconv"
)

func main() {
	var n, q int
	fmt.Scan(&n, &q)
	sc := bufio.NewScanner(os.Stdin)
	sc.Split(bufio.ScanWords)
	cs := make([]int, n)
	for i := range cs {
		sc.Scan()
		cs[i], _ = strconv.Atoi(sc.Text())
	}
	const block = 800
	qs := make([][]int, q)
	for i := range qs {
		sc.Scan()
		l, _ := strconv.Atoi(sc.Text())
		l--
		sc.Scan()
		r, _ := strconv.Atoi(sc.Text())
		r--
		lb := l % block
		qs[i] = []int{l, r, lb, i, 0}
	}
	sort.Slice(qs, func(i, j int) bool {
		if qs[i][2] == qs[j][2] {
			return qs[i][1] < qs[j][1]
		}
		return qs[i][2] < qs[j][2]
	})

	cnt := make(map[int]int)
	cl, cr := 0, -1
	t := 0
	for i := range qs {
		l, r := qs[i][0], qs[i][1]
		for j := cr + 1; j <= r; j++ {
			cnt[cs[j]]++
			if c, ok := cnt[cs[j]]; ok && c == 1 {
				t++
			}
		}
		for j := cl - 1; j >= l; j-- {
			cnt[cs[j]]++
			if c, ok := cnt[cs[j]]; ok && c == 1 {
				t++
			}
		}
		for j := cr; j > r; j-- {
			cnt[cs[j]]--
			if c, ok := cnt[cs[j]]; ok && c == 0 {
				t--
			}
		}
		for j := cl; j < l; j++ {
			cnt[cs[j]]--
			if c, ok := cnt[cs[j]]; ok && c == 0 {
				t--
			}
		}
		qs[i][4] = t
		cl, cr = l, r
	}
	sort.Slice(qs, func(i, j int) bool {
		return qs[i][3] < qs[j][3]
	})
	for i := range qs {
		fmt.Println(qs[i][4])
	}
}

func min(a, b int) int {
	if a < b {
		return a
	}
	return b
}

func max(a, b int) int {
	if a > b {
		return a
	}
	return b
}

func abs(a int) int {
	if a < 0 {
		return -a
	}
	return a
}