Add Segment Tree that takes the merge method as a template argument.

Author: xennygrimmato

Segment Tree/MergeMethodAsTemplateArg.cpp

@@ -0,0 +1,182 @@
+// Source: https://codeforces.com/contest/1436/submission/96572644
+// Was looking for a Segtree template to which I can pass something like `[&](int x, int y) {return min(x, y);}`
+// to create a segment tree.
+// Also, build, query and update are all iterative.
+// Credits to tute7627 (https://codeforces.com/profile/tute7627).
+
+//#define _GLIBCXX_DEBUG
+ 
+#include<bits/stdc++.h>
+using namespace std;
+ 
+#define endl '\n'
+#define lfs cout<<fixed<<setprecision(10)
+#define ALL(a) (a).begin(),(a).end()
+#define ALLR(a) (a).rbegin(),(a).rend()
+#define spa << " " <<
+#define fi first
+#define se second
+#define MP make_pair
+#define MT make_tuple
+#define PB push_back
+#define EB emplace_back
+#define rep(i,n,m) for(ll i = (n); i < (ll)(m); i++)
+#define rrep(i,n,m) for(ll i = (ll)(m) - 1; i >= (ll)(n); i--)
+using ll = long long;
+using ld = long double;
+const ll MOD1 = 1e9+7;
+const ll MOD9 = 998244353;
+const ll INF = 1e18;
+using P = pair<ll, ll>;
+template<typename T1, typename T2>bool chmin(T1 &a,T2 b){if(a>b){a=b;return true;}else return false;}
+template<typename T1, typename T2>bool chmax(T1 &a,T2 b){if(a<b){a=b;return true;}else return false;}
+ll median(ll a,ll b, ll c){return a+b+c-max({a,b,c})-min({a,b,c});}
+void ans1(bool x){if(x) cout<<"Yes"<<endl;else cout<<"No"<<endl;}
+void ans2(bool x){if(x) cout<<"YES"<<endl;else cout<<"NO"<<endl;}
+void ans3(bool x){if(x) cout<<"Yay!"<<endl;else cout<<":("<<endl;}
+template<typename T1,typename T2>void ans(bool x,T1 y,T2 z){if(x)cout<<y<<endl;else cout<<z<<endl;} 
+template<typename T>void debug(vector<vector<T>>&v,ll h,ll w){for(ll i=0;i<h;i++){cout<<v[i][0];for(ll j=1;j<w;j++)cout spa v[i][j];cout<<endl;}};
+void debug(vector<string>&v,ll h,ll w){for(ll i=0;i<h;i++){for(ll j=0;j<w;j++)cout<<v[i][j];cout<<endl;}};
+template<typename T>void debug(vector<T>&v,ll n){if(n!=0)cout<<v[0];for(ll i=1;i<n;i++)cout spa v[i];cout<<endl;};
+template<typename T>vector<vector<T>>vec(ll x, ll y, T w){vector<vector<T>>v(x,vector<T>(y,w));return v;}
+ll gcd(ll x,ll y){ll r;while(y!=0&&(r=x%y)!=0){x=y;y=r;}return y==0?x:y;}
+vector<ll>dx={1,-1,0,0,1,1,-1,-1};vector<ll>dy={0,0,1,-1,1,-1,1,-1};
+template<typename T>vector<T> make_v(size_t a,T b){return vector<T>(a,b);}
+template<typename... Ts>auto make_v(size_t a,Ts... ts){return vector<decltype(make_v(ts...))>(a,make_v(ts...));}
+template<typename T1, typename T2>ostream &operator<<(ostream &os, const pair<T1, T2>&p){return os << p.first << " " << p.second;}
+template<typename T>ostream &operator<<(ostream &os, const vector<T> &v){for(auto &z:v)os << z << " ";cout<<"|"; return os;}
+//mt19937 mt(chrono::steady_clock::now().time_since_epoch().count());
+int popcount(ll x){return __builtin_popcountll(x);};
+int poplow(ll x){return __builtin_ctzll(x);};
+int pophigh(ll x){return 63 - __builtin_clzll(x);};
+template< typename Monoid ,typename F>
+struct SegmentTree {
+ int sz, n;
+ vector< Monoid > seg;
+ const F f;
+ const Monoid M1;
+ 
+ SegmentTree(int n, const F f, const Monoid &M1) : f(f), M1(M1), n(n){
+ sz = 1;
+ while(sz < n) sz <<= 1;
+ seg.assign(2 * sz, M1);
+ }
+ 
+ void set(int k, const Monoid &x) {
+ seg[k + sz] = x;
+ }
+ 
+ void build() {
+ for(int k = sz - 1; k > 0; k--) {
+ seg[k] = f(seg[2 * k + 0], seg[2 * k + 1]);
+ }
+ }
+ 
+ void update(int k, const Monoid &x) {
+ k += sz;
+ seg[k] = x;
+ while(k >>= 1) {
+ seg[k] = f(seg[2 * k + 0], seg[2 * k + 1]);
+ }
+ }
+ 
+ Monoid query(int a, int b) {
+ if(a>=b)return M1;
+ Monoid L = M1, R = M1;
+ for(a += sz, b += sz; a < b; a >>= 1, b >>= 1) {
+ if(a & 1) L = f(L, seg[a++]);
+ if(b & 1) R = f(seg[--b], R);
+ }
+ return f(L, R);
+ }
+ 
+ Monoid operator[](const int &k) const {
+ return seg[k + sz];
+ }
+ 
+ template< typename C >
+ int find_subtree(int a, const C &check, Monoid &M, bool type) {
+ while(a < sz) {
+ Monoid nxt = type ? f(seg[2 * a + type], M) : f(M, seg[2 * a + type]);
+ if(check(nxt)) a = 2 * a + type;
+ else M = nxt, a = 2 * a + 1 - type;
+ }
+ return a - sz;
+ }
+ //[a,x]が条件を満たす最初のx,満たさなければ-1
+ template< typename C >
+ int find_first(int a, const C &check) {
+ Monoid L = M1;
+ if(a <= 0) {
+ if(check(f(L, seg[1]))) return find_subtree(1, check, L, false);
+ return -1;
+ }
+ int b = sz;
+ for(a += sz, b += sz; a < b; a >>= 1, b >>= 1) {
+ if(a & 1) {
+ Monoid nxt = f(L, seg[a]);
+ if(check(nxt)) return find_subtree(a, check, L, false);
+ L = nxt;
+ ++a;
+ }
+ }
+ return -1;
+ }
+ 
+ template< typename C >
+ int find_last(int b, const C &check) {
+ Monoid R = M1;
+ if(b >= sz) {
+ if(check(f(seg[1], R))) return find_subtree(1, check, R, true);
+ return -1;
+ }
+ int a = sz;
+ for(b += sz; a < b; a >>= 1, b >>= 1) {
+ if(b & 1) {
+ Monoid nxt = f(seg[--b], R);
+ if(check(nxt)) return find_subtree(b, check, R, true);
+ R = nxt;
+ }
+ }
+ return -1;
+ }
+ void print(){
+ for(ll i=0;i<n;i++)if((*this)[i]==M1)cout<<"x ";else cout<<(*this)[i]<<" ";
+ cout<<endl;
+ }
+};
+int main(){
+ cin.tie(nullptr);
+ ios_base::sync_with_stdio(false);
+ ll res=0,buf=0;
+ bool judge = true;
+ ll n;cin>>n;
+ vector<ll>a(n);
+ rep(i,0,n)cin>>a[i],a[i]--;
+ auto ff=[&](ll x,ll y){return min(x,y);};
+ SegmentTree<ll,decltype(ff)>seg(n+1,ff,LLONG_MAX);
+ vector<bool>t(n+2);
+ rep(i,0,n+1)seg.set(i,-1);
+ seg.build();
+ rep(i,0,n){
+ ll mi=seg.query(0,a[i]);
+ if(mi>seg[a[i]])t[a[i]]=true;
+ seg.update(a[i],i);
+ }
+ rep(i,0,n+1){
+ ll mi=seg.query(0,i);
+ //cout<<mi spa i spa seg[i] spa (mi>seg[i])<<endl;
+ if(mi>seg[i])t[i]=true;
+ }
+ t[0]=false;
+ rep(i,0,n){
+ if(a[i]!=0)t[0]=true;
+ }
+ rep(i,0,n+2){
+ if(!t[i]){
+ cout<<i+1<<endl;
+ return 0;
+ }
+ }
+ return 0;
+}