Codeforces 351D Jeff and Removing Periods 线段树

题目转换一下就变成询问区间里面有多少个不同数字，和区间里面有没有等差数列的相同数字。
离线之后可能分别用树状数组和线段树维护，线段树维护数字等差数列能延续到的最右端。
#include<bits/stdc++.h>
#define LL long long
#define LD long double
#define ull unsigned long long
#define fi first
#define se second
#define mk make_pair
#define PLL pair<LL, LL>
#define PLI pair<LL, int>
#define PII pair<int, int>
#define SZ(x) ((int)x.size())
#define ALL(x) (x).begin(), (x).end()
#define fio ios::sync_with_stdio(false); cin.tie(0);

using namespace std;

const int N = 2e5 + 7;
const int inf = 0x3f3f3f3f;
const LL INF = 0x3f3f3f3f3f3f3f3f;
const int mod = 998244353;
const double eps = 1e-8;
const double PI = acos(-1);

template<class T, class S> inline void add(T& a, S b) {a += b; if(a >= mod) a -= mod;}
template<class T, class S> inline void sub(T& a, S b) {a -= b; if(a < 0) a += mod;}
template<class T, class S> inline bool chkmax(T& a, S b) {return a < b ? a = b, true : false;}
template<class T, class S> inline bool chkmin(T& a, S b) {return a > b ? a = b, true : false;}

struct Bit {
    int a[N];
    void modify(int x, int v) {
        for(int i = x; i < N; i += i & -i)
            a[i] += v;
    }
    int sum(int x) {
        int ans = 0;
        for(int i = x; i; i -= i & -i)
            ans += a[i];
        return ans;
    }
    int query(int L, int R) {
        if(L > R) return 0;
        return sum(R) - sum(L - 1);
    }
} bit;

#define lson l, mid, rt << 1
#define rson mid + 1, r, rt << 1 | 1

struct segmentTree {
    int mx[N << 2];
    void modify(int p, int val, int l, int r, int rt) {
        if(l == r) {
            mx[rt] = val;
            return;
        }
        int mid = l + r >> 1;
        if(p <= mid) modify(p, val, lson);
        else modify(p, val, rson);
        mx[rt] = max(mx[rt << 1], mx[rt << 1 | 1]);
    }
    int query(int L, int R, int l, int r, int rt) {
        if(R < l || r < L || R < L) return 0;
        if(L <= l && r <= R) return mx[rt];
        int mid = l + r >> 1;
        return max(query(L, R, lson), query(L, R, rson));
    }
} Tree;

int n, q, b[N], ans[N];
int L[N], R[N], Map[N];
int to[N], dif[N], nex[N];

vector<int> qus[N];

int main() {
    scanf("%d", &n);
    for(int i = 1; i <= n; i++) scanf("%d", &b[i]);
    scanf("%d", &q);
    for(int i = 1; i <= q; i++) {
        scanf("%d%d", &L[i], &R[i]);
        qus[L[i]].push_back(i);
    }
    for(int i = n; i >= 1; i--) {
        if(Map[b[i]]) bit.modify(Map[b[i]], -1);
        bit.modify(i, 1);
        Map[b[i]] = i;
        for(auto& id : qus[i]) ans[id] = bit.query(L[id], R[id]) + 1;
    }
    memset(Map, 0, sizeof(Map));
    for(int i = n; i >= 1; i--) {
        if(Map[b[i]]) {
            int j = Map[b[i]];
            nex[i] = j;
            if(dif[j] == -1) {
                to[i] = to[j];
                dif[i] = j - i;
                Tree.modify(i, to[i], 1, n, 1);
                Tree.modify(j, 0, 1, n, 1);
            } else {
                if(j - i == dif[j]) {
                    to[i] = to[j];
                    dif[i] = j - i;
                    Tree.modify(i, to[i], 1, n, 1);
                    Tree.modify(j, 0, 1, n, 1);
                } else {
                    to[i] = nex[j] - 1;
                    dif[i] = j - i;
                    Tree.modify(i, to[i], 1, n, 1);
                    Tree.modify(j, 0, 1, n, 1);
                }
            }
        } else {
            nex[i] = n + 1;
            to[i] = n + 1;
            dif[i] = -1;
            Tree.modify(i, to[i], 1, n, 1);
        }
        for(auto& id : qus[i]) {
            if(Tree.query(L[id], R[id], 1, n, 1) >= R[id]) ans[id]--;
        }
        Map[b[i]] = i;
    }
    for(int i = 1; i <= q; i++) printf("%d
", ans[i]);
    return 0;
}

/*
*/