459D - Pashmak and Parmida's problem - CodeForces Solution

#include <bits/stdc++.h>
#define MAX 1000001
#define INF 2e9
#define MOD 1000000007
#define mp make_pair
#define mt make_tuple
#define pb push_back
#define ins insert
#define ff first
#define ss second
#define gett(x,m) get<m>(x)
#define all(a) a.begin(),a.end()
#define lb(a,b) lower_bound(all(a),b)
#define ub(a,b) upper_bound(all(a),b)
#define sortv(a) sort(all(a))
#define sorta(a,sz) sort(a,a+sz)
#define inputar(a,b){\
    for(int i=0;i<b;i++){\
        cin >> a[i];\
    }\
}
#define inputvec(a,b){\
    for(int i=0;i<b;i++){\
        ll num;\
        cin >> num;\
        a.pb(num);\
    }\
}
#define outputar(a,b){\
    for(int i=0;i<b;i++){\
        cout << a[i] << " ";\
    }\
    cout << "\n";\
}
#define outputvec(a){\
    for(auto x:a){\
        cout << x << " ";\
    }\
    cout << "\n";\
}
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef double db;
typedef long double ldb;
typedef tuple<ll,ll,ll> tll;
typedef pair<ll,ll> pll;
typedef pair<int,int> pii;
inline void USACO(string filename){
  freopen((filename+".in").c_str(),"r",stdin);
  freopen((filename+".out").c_str(),"w",stdout);
}
ll n,q,t=1,m,n2,m2,k,cnt=0,a[MAX],b[MAX],d[MAX],x,y,z,x2,y2,z2,res1=0,cnt1,cnt2,cnt3;
ll c[501][501];
ll fact[MAX];
ll inv_fact[MAX];
//char c;
string str[MAX];
string s1,s2;
vector<tuple<ll,ll,ll>> v;
vector<pll> v1,v2,v3,v4;
const int mod = 998244353;
ll modmul(ll x,ll y,ll md){
    if(y==1){
        return x;
    }
    if(y%2){
        return (x+modmul(x,y-1,md))%md;
    }
    else{
        return (modmul((x+x)%md,y/2,md))%md;
    }
}
ll powmod(ll x,ll y,ll md){
    x%=md;
    if(x==0){
        return 0;
    }
    ll res=1;
    while(y){
        if(y%2==1){
            //res=modmul(res,x,md);
            res*=x;
            res%=MOD;
            y--;
        }
        else{
            //x=modmul(x,x,md);
            x*=x;
            x%=MOD;
            y/=2;
        }
    }
    return res;
}
ll pow2(ll x,ll y){
    if(x==0){
        return 0;
    }
    ll res=1;
    while(y>0){
        if(y%2==1){
            res*=x;
        }
        x*=x;
        y/=2;
    }
    return res;
}
ll inv(ll n,ll md){
    return powmod(n,md-2,md);
}
ll nCkm(ll n,ll k,ll md){
    if(n-k<0){
        return 0;
    }
    return fact[n]*inv_fact[k]%md*inv_fact[n-k]%md;
}
ll nCk(ll x,ll y){
    if(x<y){
        return 0;
    }
    ll res=1;
    if(y>x-y){
        for(int i=y+1;i<=x;i++){
            res*=i;
        }
        for(int i=2;i<=x-y;i++){
            res/=i;
        }
    }
    else{
        for(int i=x-y+1;i<=x;i++){
            res*=i;
        }
        for(int i=2;i<=y;i++){
            res/=i;
        }
    }
    return res;
}
ll countbits(ll x){
    ll cnt=0;
    while(x){
        cnt+=x&1;
        x>>=1;
    }
    return cnt;
}
ll gcd(ll x,ll y){
    if(y==0){
        return x;
    }
    return gcd(y,x%y);
}
ll lcm(ll x,ll y){
    return x*y/gcd(x,y);
}
bool alpha(char c1,char c2){
    ll h1,h2;
    if(c1>='a'){
        h1=c1-'a';
    }
    else{
        h1=c1-'A';
    }
    if(c2>='a'){
        h2=c2-'a';
    }
    else{
        h2=c2-'A';
    }
    if(h1==h2){
        return c1<c2;
    }
    else{
        return h1<h2;
    }
}
ll dx[8]={1,2,2,1,-1,-2,-2,-1};
ll dy[8]={-2,-1,1,2,2,1,-1,-2};
struct custom_hash {
   static uint64_t splitmix64(uint64_t x) {
        x += 0x9e3779b97f4a7c15;
        x = (x ^ (x >> 30)) * 0xbf58476d1ce4e5b9;
        x = (x ^ (x >> 27)) * 0x94d049bb133111eb;
        return x ^ (x >> 31);
    }

    size_t operator()(uint64_t x) const {
        static const uint64_t FIXED_RANDOM = chrono::steady_clock::now().time_since_epoch().count();
        return splitmix64(x + FIXED_RANDOM);
    }
};
struct segtree{
    int size;
    vector<ll> sums;
    void build(vector<int> &a,int x,int lx,int rx){
        if(rx-lx==1){
            if(lx<(int)a.size()){
                sums[x]=a[lx];
            }
            return;
        }
        int m=(lx+rx)/2;
        build(a,2*x+1,lx,m);
        build(a,2*x+2,m,rx);
        sums[x]=sums[2*x+1]+sums[2*x+2];
    }
    void build(vector<int> &a){
        build(a,0,0,size);
    }
    void init(int n){
        size=1;
        while(size<n){
            size*=2;
        }
        sums.assign(2*size,0LL);
    }
    ll sum(int l,int r,int x,int lx,int rx){
        if(lx>=r || rx<=l){
            return 0;
        }
        if(lx>=l && rx<=r){
            return sums[x];
        }
        ll s1,s2;
        int m=(lx+rx)/2;
        s1=sum(l,r,2*x+1,lx,m);
        s2=sum(l,r,2*x+2,m,rx);
        return s1+s2;
    }
    ll sum(int l,int r){
        return sum(l,r,0,0,size);
    }
    void set(int i,int v,int x,int lx,int rx){
        if(rx-lx==1){
            sums[x]=v;
            return;
        }
        int m=(lx+rx)/2;
        if(i<m){
            set(i,v,2*x+1,lx,m);
        }
        else{
            set(i,v,2*x+2,m,rx);
        }
        sums[x]=sums[2*x+1]+sums[2*x+2];
    }
    void set(int i,int v){
        set(i,v,0,0,size);
    }
};
int sum[MAX];
void update(int x,int v){
    while(x<=n){
        sum[x]+=v;
        x+=x&-x;
    }
}
int query(int x){
    ll res=0;
    while(x>=1){
        res+=sum[x];
        x-=x&-x;
    }
    return res;
}
void solve(){
    cin >> n;
    inputar(a,n);
    unordered_map<int,int,custom_hash> c;
    for(int i=0;i<n;i++){
        c[a[i]]++;
        b[i]=c[a[i]];
    }
    c.clear();
    for(int i=n-1;i>=0;i--){
        c[a[i]]++;
        d[i]=c[a[i]];
    }
    vector<pii> v1;
    vector<pii> v2;
    for(int i=0;i<n;i++){
        v1.pb(mp(b[i],i+1));
    }
    for(int i=0;i<n;i++){
        v2.pb(mp(d[i],i+1));
    }
    sortv(v1);
    sortv(v2);
    reverse(all(v1));
    reverse(all(v2));
    int j=0;
    ll res=0;
    for(int i=0;i<n;i++){
        while(j<n && v2[j].ff>=v1[i].ff){
            update(v2[j].ss,-1);
            j++;
        }
        int sum=query(n)-query(v1[i].ss);
        res+=n-v1[i].ss+sum;
    }
    cout << res << "\n";
}
int main(){
    ios::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    //USACO("angry");
    //freopen("input.txt","r",stdin);
    //cin >> t;
    ll cnt1=1;
    while(t--){
        solve();
        cnt1++;
    }
}
/*
freopen("input.txt","r",stdin);
freopen("output.txt","w",stdout);
ifstream fin("template.in");
ofstream fout("template.out");
*/
/*
freopen("input.txt","r",stdin);
freopen("output.txt","w",stdout);
ifstream fin("template.in");
ofstream fout("template.out");
*/
/*
ll b[51][51];
b[0][0] = 1;
    for (int n = 1; n <= 50; ++n){
        b[n][0] = b[n][n] = 1;
        for (int k = 1; k < n; ++k)
            b[n][k] = b[n - 1][k - 1] + b[n - 1][k];
    }
*/