Submission #1305687

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Source Code Expand

#include <bits/stdc++.h>
using namespace std;

typedef long long ll;
typedef pair<int,int> pii;
typedef pair<ll,int> plli;
typedef pair<int,pii> pipii;
typedef vector<int> vi;
typedef vector<ll> vll;
typedef vector<vi> vvi;
typedef vector<vvi> vvvi;
typedef vector<pii> vpii;

#define rep(i,n) for (int i=0;i<(n);i++)
#define rep2(i,a,b) for (int i=(a);i<(b);i++)
#define rrep(i,n) for (int i=(n);i>=0;i--)
#define rrep2(i,a,b) for (int i=(a);i>b;i--)
#define pb push_back
#define fi first
#define se second
#define all(a) (a).begin(),(a).end()

const ll mod = 1e9 + 7;
const ll INF = 1<<30;
const int dx[4] = {1, 0, -1, 0};
const int dy[4] = {0, 1, 0, -1};
const double pi = 3.141592653589793;

class UnionFind{
    private:
        vector<ll> parent,rank,tree_w;
    public:
        UnionFind(int size){
            for (int i=0; i<size; i++){
                parent.push_back(i);
                rank.push_back(0);
                tree_w.push_back(1);
            }
        }

        int findset(int x){
            return x==parent[x] ? x : parent[x]=findset(parent[x]);
        }

        void unite(int x,int y){
            x=findset(x);y=findset(y);
            if (x==y) return;
            if (rank[x]>rank[y]) swap(x,y);
            parent[x]=y;
            tree_w[y]+=tree_w[x];
            if (rank[x]==rank[y]) rank[y]+=1;
        }

        ll tree_weight(int x){
            return tree_w[findset(x)];
        }
};

ll n;
ll a[200000+5];
ll pos[200000+5];
bool check[200000+5];

int main(){
    cin.tie(0);
    ios::sync_with_stdio(false);
    cin >> n;
    rep(i,n){
        cin >> a[i];
        a[i]--;
    }
    rep(i,n) pos[a[i]]=i;
    UnionFind uf(n);
    ll ans=0LL;
    rrep(i,n-1){
        ll l=max<ll>(pos[i]-1,0);
        ll r=min<ll>(pos[i]+1,n-1);
        ll lnum=1LL;
        ll rnum=1LL;
        if (check[l]){
            lnum+=uf.tree_weight(l);
        }
        if (check[r]){
            rnum+=uf.tree_weight(r);
        }
        if (check[l]){
            uf.unite(l,pos[i]);
        }
        if (check[r]){
            uf.unite(r,pos[i]);
        }
        check[pos[i]]=true;
        ans+=(i+1)*lnum*rnum;
    }
    cout << ans << endl;
    return 0;
}

Submission Info

Judge Result