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 Rust (1.42.0) (judge verdict: Accepted)

use std::cmp::*;
use input_mcr::*;
use bit::*;
use std::collections::HashMap;

fn main() {
    input! {
        n: usize,
        q: usize,
        xs: [usize1; n],
        qs: [(usize1,usize1); q],
    }
    let mut prev = vec![0; n];
    let mut rs = vec![];
    for (i, &x) in xs.iter().enumerate() {
        if prev[x] != 0 {
            rs.push((prev[x]-1,i+1,0));
        }
        prev[x] = i+1;
    }
    for &(l,r) in &qs {
        rs.push((l,r+1,1));
    }
    rs.sort_by(|x,y| (x.1,x.2,x.0).cmp(&(y.1,y.2,y.0)));
    // eprintln!("rs = {:?}", rs);
    let mut bit = BIT::new(2*n+1);
    let mut res: HashMap<(usize,usize),i64> = HashMap::new();
    for &(l,r,q) in &rs {
        if q == 0 {
            bit.add(l + 1, 1);
            // bit.add(r + 1, -1);
        }
        if q == 1 {
            let t = bit.sum(r + 1) - bit.sum(l + 1 - 1);
            // eprintln!("l = {}, r = {}, t = {}", l, r, t);
            res.insert((l,r), (r-l) as i64 - t);
        }
    }
    for &(l,r) in &qs {
        println!("{}", res[&(l,r+1)]);
    }
}
pub mod input_mcr {
    // ref: tanakh <https://qiita.com/tanakh/items/0ba42c7ca36cd29d0ac8>
    #[macro_export(local_inner_macros)]
    macro_rules! input {
        (source = $s:expr, $($r:tt)*) => {
            let mut parser = Parser::from_str($s);
            input_inner!{parser, $($r)*}
        };
        (parser = $parser:ident, $($r:tt)*) => {
            input_inner!{$parser, $($r)*}
        };
        (new_stdin_parser = $parser:ident, $($r:tt)*) => {
            let stdin = std::io::stdin();
            let reader = std::io::BufReader::new(stdin.lock());
            let mut $parser = Parser::new(reader);
            input_inner!{$parser, $($r)*}
        };
        ($($r:tt)*) => {
            input!{new_stdin_parser = parser, $($r)*}
        };
    }
    
    #[macro_export(local_inner_macros)]
    macro_rules! input_inner {
        ($parser:ident) => {};
        ($parser:ident, ) => {};
        ($parser:ident, $var:ident : $t:tt $($r:tt)*) => {
            let $var = read_value!($parser, $t);
            input_inner!{$parser $($r)*}
        };
    }
    
    #[macro_export(local_inner_macros)]
    macro_rules! read_value {
        ($parser:ident, ( $($t:tt),* )) => {
            ( $(read_value!($parser, $t)),* )
        };
        ($parser:ident, [ $t:tt ; $len:expr ]) => {
            (0..$len).map(|_| read_value!($parser, $t)).collect::<Vec<_>>()
        };
        ($parser:ident, chars) => {
            read_value!($parser, String).chars().collect::<Vec<char>>()
        };
        ($parser:ident, char_) => {
            read_value!($parser, String).chars().collect::<Vec<char>>()[0]
        };
        ($parser:ident, usize1) => {
            read_value!($parser, usize) - 1
        };
        ($parser:ident, line) => {
            $parser.next_line()
        };
        ($parser:ident, line_) => {
            $parser.next_line().chars().collect::<Vec<char>>()
        };
        ($parser:ident, $t:ty) => {
            $parser.next::<$t>().expect("Parse error")
        };
    }
    
    use std::io;
    use std::io::BufRead;
    use std::str;
    use std::collections::VecDeque;
    
    pub struct Parser<R> {
        pub reader: R,
        buf: VecDeque<u8>,
        parse_buf: Vec<u8>,
    }
    
    impl Parser<io::Empty> {
        pub fn from_str(s: &str) -> Parser<io::Empty> {
            Parser {
                reader: io::empty(),
                buf: VecDeque::from(s.as_bytes().to_vec()),
                parse_buf: vec![],
            }
        }
    }
    
    impl<R: BufRead> Parser<R> {
        pub fn new(reader: R) -> Parser<R> {
            Parser {
                reader: reader,
                buf: VecDeque::new(),
                parse_buf: vec![],
            }
        }
        pub fn update_buf(&mut self) {
            loop {
                let (len, complete) = {
                    let buf2 = self.reader.fill_buf().unwrap();
                    self.buf.extend(buf2.iter());
                    let len = buf2.len();
                    (len, buf2.last() < Some(&0x20))
                };
                self.reader.consume(len);
                if complete {
                    break;
                }
            }
        }
        pub fn next<T: str::FromStr>(&mut self) -> Result<T, T::Err> {
            loop {
                while let Some(c) = self.buf.pop_front() {
                    if c > 0x20 {
                        self.buf.push_front(c);
                        break;
                    }
                }
                self.parse_buf.clear();
                while let Some(c) = self.buf.pop_front() {
                    if c <= 0x20 {
                        self.buf.push_front(c);
                        break;
                    } else {
                        self.parse_buf.push(c);
                    }
                }
                if self.parse_buf.is_empty() {
                    self.update_buf();
                } else {
                    return unsafe { str::from_utf8_unchecked(&self.parse_buf) }.parse::<T>();
                }
            }
        }
        pub fn next_line(&mut self) -> String {
            loop {
                while let Some(c) = self.buf.pop_front() {
                    if c >= 0x20 {
                        self.buf.push_front(c);
                        break;
                    }
                }
                self.parse_buf.clear();
                while let Some(c) = self.buf.pop_front() {
                    if c < 0x20 {
                        self.buf.push_front(c);
                        break;
                    } else {
                        self.parse_buf.push(c);
                    }
                }
                if self.parse_buf.is_empty() {
                    self.update_buf();
                } else {
                    return unsafe { str::from_utf8_unchecked(&self.parse_buf) }.to_string();
                }
            }
        }
    }
}
pub mod bit {
    #[derive(Debug,Clone)]
    pub struct BIT {
        xs: Vec<i64>,
        n: usize,
    }
    
    // 1-indexed !!!
    impl BIT {
        pub fn new(n: usize) -> BIT {
            BIT {
                xs: vec![0; n + 1],
                n: n,
            }
        }
        pub fn sum(&self, i: usize) -> i64 {
            let mut res = 0;
            let mut i = i;
            while i > 0 {
                res += self.xs[i];
                i -= i & !(i - 1);
            }
            res
        }
        pub fn add(&mut self, i: usize, x: i64) {
            let mut i = i;
            while i <= self.n {
                self.xs[i] += x;
                i += i & !(i - 1);
            }
        }
        // return <= i
        pub fn max_non_zero_index(&self, i: usize) -> usize {
            let mut d = 1 << 28;
            let mut i = i;
            while d != 0 {
                if i < d {
                    d /= 2;
                    continue;
                }
                if self.sum(i - d) == self.sum(i) {
                    i = i - d;
                }
                d /= 2;
            }
            i
        }
        pub fn min_non_zero_index(&self, i: usize) -> usize {
            let mut d = 1 << 28;
            let mut i = i;
            while d != 0 {
                if i + d > self.n {
                    d /= 2;
                    continue;
                }
                if self.sum(i + d) == self.sum(i) {
                    i = i + d;
                }
                d /= 2;
            }
            i + 1
        }
    }
    
    #[test]
    fn test_bit_1() {
        let mut bit = BIT::new(6);
        bit.add(1, 1);
        bit.add(2, 1);
        bit.add(4, 1);
        assert_eq!(bit.max_non_zero_index(1), 1);
        assert_eq!(bit.max_non_zero_index(2), 2);
        assert_eq!(bit.max_non_zero_index(3), 2);
        assert_eq!(bit.max_non_zero_index(4), 4);
        assert_eq!(bit.max_non_zero_index(5), 4);
        assert_eq!(bit.max_non_zero_index(6), 4);
    }
}