codeforces 1000F One Occurrence
#include<bits/stdc++.h> using namespace std; #define fi first #define se second #define mp make_pair #define pb push_back #define rep(i, a, b) for(int i=(a); i<(b); i++) #define sz(a) (int)a.size() #define de(a) cout << #a << " = " << a << endl #define dd(a) cout << #a << " = " << a << " " #define all(a) a.begin(), a.end() #define endl "\n" typedef long long ll; typedef pair<int, int> pii; typedef vector<int> vi; //--- const int N = 500050; int n, m; int a[N], ans[N], nx[N], vis[N]; bool in[N]; vector<pii> q[N]; struct Seg { #define ls (rt<<1) #define rs (ls|1) static const int N = ::N*4+22; int ma[N], ind[N]; void upd(int p, int c, int l, int r, int rt) { if(l == r) { ma[rt] = c; ind[rt] = l; return ; } int mid = l+r>>1; if(p<=mid) upd(p, c, l, mid, ls); else upd(p, c, mid+1, r, rs); ma[rt] = max(ma[ls], ma[rs]); ind[rt] = ma[ls]>ma[rs] ? ind[ls] : ind[rs]; } void upd(pii &a, pii b) { if(a < b) a = b; } pii qry(int L, int R, int l, int r, int rt) { if(L<=l && r<=R) return mp(ma[rt], a[ind[rt]]); int mid = l+r>>1; pii ans = mp(0, 0); if(L<=mid) upd(ans, qry(L, R, l, mid, ls)); if(R>=mid+1) upd(ans, qry(L, R, mid+1, r, rs)); return ans; } }seg; int main() { std::ios::sync_with_stdio(false); std::cin.tie(0); ///read cin >> n; rep(i, 1, n+1) cin >> a[i]; cin >> m; rep(i, 1, m+1) { int x, y; cin >> x >> y; q[x].pb(mp(y, i)); } ///solve for(int i = n; i; --i) { nx[i] = vis[a[i]]; if(!nx[i]) nx[i] = n+1; vis[a[i]] = i; } memset(vis, 0, sizeof(vis)); rep(i, 1, n+1) vis[nx[i]] = 1; rep(i, 1, n+1) if(!vis[i]) seg.upd(i, nx[i], 1, n, 1); rep(i, 1, n+1) { for(auto t : q[i]) { auto c = seg.qry(i, t.fi, 1, n, 1); ans[t.se] = c.fi>t.fi ? c.se : 0; } if(nx[i]<=n) seg.upd(nx[i], nx[nx[i]], 1, n, 1); } rep(i, 1, m+1) cout << ans[i] << endl; return 0; }#include<bits/stdc++.h> using namespace std; #define fi first #define se second #define mp make_pair #define pb push_back #define rep(i, a, b) for(int i=(a); i<(b); i++) #define sz(a) (int)a.size() #define de(a) cout << #a << " = " << a << endl #define dd(a) cout << #a << " = " << a << " " #define all(a) a.begin(), a.end() #define endl "\n" typedef long long ll; typedef pair<int, int> pii; typedef vector<int> vi; //--- const int N = 505050; int n, m; int a[N], ans[N], ne[N], vis[N]; vector<pii> q[N]; struct Seg { #define ls (rt<<1) #define rs (ls|1) static const int N = ::N<<2; int pri[N], val[N], p, v; void upd(int L, int R, int p, int v, int l, int r, int rt) { if(L<=l && r<=R) { if(p > pri[rt]) { pri[rt] = p; val[rt] = v; } return ; } int mid = l+r>>1; if(L<=mid) upd(L, R, p, v, l, mid, ls); if(R>=mid+1) upd(L, R, p, v, mid+1, r, rs); } void _qry(int pos, int l, int r, int rt) { if(pri[rt] > p) { p = pri[rt]; v = val[rt]; } if(l == r) return ; int mid = l+r>>1; if(pos<=mid) _qry(pos, l, mid, ls); else _qry(pos, mid+1, r, rs); } pii qry(int pos) { p = v = 0; _qry(pos, 1, n, 1); return mp(p, v); } }seg; int main() { std::ios::sync_with_stdio(false); std::cin.tie(0); cin >> n; rep(i, 1, n+1) cin >> a[i]; cin >> m; rep(i, 1, m+1) { int x, y; cin >> x >> y; q[x].pb(mp(y, i)); } for(int i = n; i; --i) { ne[i] = vis[a[i]]; vis[a[i]] = i; if(!ne[i]) ne[i] = n+1; } memset(vis, 0, sizeof(vis)); rep(i, 1, n+1) vis[ne[i]] = 1; rep(i, 1, n+1) if(!vis[i]) seg.upd(i, ne[i] - 1, i, a[i], 1, n, 1); rep(i, 1, n+1) { for(auto j : q[i]) { pii t = seg.qry(j.fi); ans[j.se] = t.fi >= i ? t.se : 0; } if(ne[i]<=n) seg.upd(ne[i], ne[ne[i]] - 1, ne[i], a[i], 1, n, 1); } rep(i, 1, m+1) cout << ans[i] << endl; return 0; }codeforces 1000F One Occurrence
原文：https://www.cnblogs.com/wuyuanyuan/p/9240463.html