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 proconio::*;
use proconio::marker::*;

pub trait MoOperator {
    type Value;
    type Query;
    type Answer;
    fn init(&mut self);
    fn insert(&mut self, v: &Self::Value);
    fn snap(&mut self);
    fn rollback(&mut self, v: &Self::Value);
    fn answer(&mut self, q: Self::Query) -> Self::Answer;
}

struct MoSolver<S: MoOperator> {
    size: usize,
    query: Vec<(usize, usize, S::Query)>,
}

impl<S: MoOperator> MoSolver<S> {
    fn new(size: usize) -> Self {
        MoSolver {
            size: size,
            query: vec![],
        }
    }
    fn add(&mut self, l: usize, r: usize, q: S::Query) {
        assert!(l < r && r <= self.size);
        self.query.push((l, r, q));
    }
    fn solve(&mut self, mut state: S, array: &[S::Value], answer: &mut [S::Answer]) {
        assert!(self.size <= array.len() && self.query.len() <= answer.len());
        if self.query.is_empty() {
            return;
        }
        let size = self.size;
        let batch = (size as f64 / (self.query.len() as f64).sqrt()).ceil() as usize;
        let mut q = vec![];
        std::mem::swap(&mut q, &mut self.query);
        let mut query = (0..(size / batch)).map(|_| vec![]).collect::<Vec<_>>();
        state.init();
        state.snap();
        for (i, (l, r, op)) in q.into_iter().enumerate() {
            if r - l <= batch {
                for v in array[l..r].iter() {
                    state.insert(v);
                }
                answer[i] = state.answer(op);
                for v in array[l..r].iter().rev() {
                    state.rollback(v);
                }
            } else {
                query[l / batch].push((r, l, i, op));
            }
        }
        for (i, mut query) in query.into_iter().enumerate() {
            state.init();
            query.sort_unstable_by_key(|p| p.0);
            let mid = (i + 1) * batch;
            let mut t = mid;
            for (r, l, k, op) in query.into_iter() {
                for v in array[t..r].iter() {
                    state.insert(v);
                }
                state.snap();
                for v in array[l..mid].iter().rev() {
                    state.insert(v);
                }
                answer[k] = state.answer(op);
                for v in array[l..mid].iter() {
                    state.rollback(v);
                }
            }
        }
    }
}

struct State {
    elem: Vec<usize>,
    memo: Vec<usize>,
    cnt: usize,
}

impl MoOperator for State {
    type Value = usize;
    type Query = ();
    type Answer = usize;
    fn init(&mut self) {
        self.elem.iter_mut().for_each(|e| *e = 0);
        self.memo.clear();
        self.cnt = 0;
    }
    fn insert(&mut self, x: &Self::Value) {
        let q = *x / 64;
        let r = *x % 64;
        let e = &mut self.elem[q];
        if *e >> r & 1 == 0 {
            *e |= 1 << r;
            self.cnt += 1;
            self.memo.push(*x);
        }
    }
    fn snap(&mut self) {
        self.memo.clear();
    }
    fn rollback(&mut self, _x: &Self::Value) {
        self.cnt -= self.memo.len();
        for &x in self.memo.iter() {
            self.elem[x / 64] ^= 1 << (x % 64);
        }
        self.memo.clear();
    }
    fn answer(&mut self, _q: Self::Query) -> usize {
        self.cnt
    }
}

#[fastout]
fn run() {
    input! {
        n: usize,
        q: usize,
        c: [Usize1; n],
        ask: [(Usize1, usize); q],
    }
    let batch = (n as f64 / (q as f64).sqrt()).ceil() as usize;
    let mut ans = vec![0; q];
    let mut query = vec![vec![]; n / batch + 1];
    let mut state = State {
        elem: vec![0; n / 64 + 1],
        memo: vec![],
        cnt: 0,
    };
    for (i, (l, r)) in ask.into_iter().enumerate() {
        if r - l <= batch {
            for v in c[l..r].iter() {
                state.insert(v);
            }
            ans[i] = state.answer(());
            state.rollback(&0);
            for v in c[l..r].iter().rev() {
                state.rollback(v);
            }
        } else {
            query[l / batch].push((r, l, i));
        }
    }
    for (i, mut query) in query.into_iter().enumerate() {
        query.sort_unstable_by_key(|p| p.0);
        let mid = (i + 1) * batch;
        let mut t = mid;
        state.init();
        for (r, l, k) in query {
            for v in c[t..r].iter() {
                state.insert(v);
            }
            t = r;
            state.snap();
            for v in c[l..mid].iter().rev() {
                state.insert(v);
            }
            ans[k] = state.answer(());
            for v in c[l..mid].iter() {
                state.rollback(v);
            }
        }
    }
    for a in ans {
        println!("{}", a);
    }
}

fn main() {
    run();
}