题意

题目链接

Sol

感觉自己已经老的爬不动了。。

想了一会儿，大概用个不删除莫队+带撤销并查集就能搞了吧，\(n \sqrt{n} logn\)应该卡的过去

不过不删除莫队咋写来着？。。。。跑去学。。

带撤销并查集咋写来着？。。。。跑去学。。。

发现自己的带撤销并查集是错的，，自己yy着调了1h终于过了大数据。。

#include<bits/stdc++.h>
#define Pair pair<int, int>
#define MP(x, y) make_pair(x, y)
#define fi first
#define se second
//#define int long long
#define LL long long
#define Fin(x) {freopen(#x".in","r",stdin);}
#define Fout(x) {freopen(#x".out","w",stdout);}
#define pb(x) push_back(x)
using namespace std;
const int mod = 1e9 + 7;
const int MAXN = 1e6 + 10;
template <typename A, typename B> inline bool chmin(A &a, B b){if(a > b) {a = b; return 1;} return 0;}
template <typename A, typename B> inline bool chmax(A &a, B b){if(a < b) {a = b; return 1;} return 0;}
template <typename A, typename B> inline LL add(A x, B y) {if(x + y < 0) return x + y + mod; return x + y >= mod ? x + y - mod : x + y;}
template <typename A, typename B> inline void add2(A &x, B y) {if(x + y < 0) x = x + y + mod; else x = (x + y >= mod ? x + y - mod : x + y);}
template <typename A, typename B> inline LL mul(A x, B y) {return 1ll * x * y % mod;}
template <typename A, typename B> inline void mul2(A &x, B y) {x = (1ll * x * y % mod + mod) % mod;}
template <typename A> inline void debug(A a){cout << a << '\n';}
template <typename A> inline LL sqr(A x){return 1ll * x * x;}
inline int read() {char c = getchar(); int x = 0, f = 1;while(c < '0' || c > '9') {if(c == '-') f = -1; c = getchar();}while(c >= '0' && c <= '9') x = x * 10 + c - '0', c = getchar();return x * f;
}
int N, M, a[MAXN], belong[MAXN], block, ans[MAXN], cnt, fa[MAXN];
struct Q {int l, r, id;bool operator < (const Q &rhs) const{return r < rhs.r;}
};
vector<Q> q[MAXN];
int SolveBlock(int x, int y) {if(x == y) return 1;vector<int> v;for(int i = x; i <= y; i++) v.pb(a[i]);sort(v.begin(), v.end());int res = 1, now = 1; for(int i = 1; i < v.size(); i++) now = (v[i] == v[i - 1] + 1 ? now + 1 : 1), chmax(res, now);return res;
}
int inder[MAXN], Top, ha[MAXN], cur, mx;
struct Node {int x, deg;
}S[MAXN];
int find(int x) {return fa[x] == x ? x : find(fa[x]);
}
void unionn(int x, int y) {x = find(x); y = find(y);if(x == y) return;if(inder[x] < inder[y]) swap(x, y);chmax(mx, inder[x] + inder[y]);fa[y] = x;S[++Top] = (Node) {y, inder[y]};S[++Top] = (Node) {x, inder[x]};//taginder[x] += inder[y];
}
void Delet(int cur) {while(Top > cur) {Node pre = S[Top--];fa[pre.x] = pre.x;inder[pre.x] = pre.deg;}
}
void Add(int x) {ha[x] = 1;if(ha[x - 1]) unionn(x - 1, x);if(ha[x + 1]) unionn(x, x + 1);
}
void solve(int i, vector<Q> &v) {memset(ha, 0, sizeof(ha));Top = 0; int R = min(N, i * block) + 1;int ql = R, qr = ql - 1;//tagcur = 0, mx = 1;for(int i = 1; i <= N; i++) fa[i] = i, inder[i] = 1;for(int i = 0; i < v.size(); i++) {Q x = v[i];while(qr < x.r) Add(a[++qr]);cur = mx; int pre = Top;while(ql > x.l) Add(a[--ql]);ans[x.id] = mx;mx = cur;Delet(pre);while(ql < R) ha[a[ql++]] = 0;}
}
signed main() {int mx = 0;N = read(); M = read(); block = sqrt(N); for(int i = 1; i <= N; i++) a[i] = read(), belong[i] = (i - 1) / block + 1, chmax(mx, belong[i]);for(int i = 1; i <= M; i++) {int x = read(), y = read();if(belong[x] == belong[y]) ans[i] = SolveBlock(x, y);else q[belong[x]].push_back({x, y, i});}for(int i = 1; i <= mx; i++) sort(q[i].begin(), q[i].end()), solve(i, q[i]);    for(int i = 1; i <= M; i++) printf("%d\n", ans[i]);return 0;
}
/*
8 3
3 1 7 2 4 5 8 6
1 6
1 3
2 4
*/