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\n", ans[i]); return 0; } /* */