Submission #250705

#	Time	Username	Problem	Language	Result	Execution time	Memory
250705		Blagojce	Mountains (NOI20_mountains)	C++11	22 / 100	108 ms	10952 KiB

Mountains

#include <bits/stdc++.h> 
#define fr(i, n, m) for(int i = (n); i < (m); i ++)
#define pb push_back
#define st first
#define nd second
#define pq priority_queue
#define all(x) begin(x), end(x)
#include <time.h>
#include <cmath>

using namespace std;
typedef long long ll;
typedef long double ld;
typedef pair<int,int> pii;

const int i_inf = 1e9;
const ll inf = 1e18;
const ll mod = 1000000007;
const ld eps = 1e-13;
const ld pi  = 3.14159265359;
 
mt19937 _rand(time(NULL));
clock_t timer = clock();
const int mxn = 5e5;
 
const ll A = 911382323;
const ll B = 972663749;
 
ll modpow(ll x, ll n){
	if(n == 0) return 1%mod;
	ll u = modpow(x, n/2);
	u = (u * u) % mod;
	if(n % 2) u = (u * x) % mod;
	return u;
}
ll inverse(ll x){
	return modpow(x, mod-2);
}
ll add(ll ans, ll val){
	ans = (ans + val) % mod;
	return ans;
}
ll mul(ll ans, ll val){
	ans = (ans * val) % mod;
	return ans;
}
ll sub(ll ans, ll val){
	ans = (ans - val) % mod;
	if(ans < 0) ans += mod;
	return ans;
}
ll _div(ll ans, ll val){
	ans = (ans * inverse(val)) % mod;
	return ans;
}
ll fakt[mxn];
ll bc(ll n, ll k){
	return (fakt[n]*inverse((fakt[k]*fakt[n-k])%mod))%mod;
}
ll sq(ll x){
	return x*x;
}
ll rsum(ll a, ll b){
	return (b-a+1)*(a+b)/2;
}
void prec(){
	fakt[0] = 1;
	fr(i, 1, mxn){
		fakt[i] = mul(fakt[i-1], i);
	}
}

int bit[mxn];
void update(int k, int val){
	while(k < mxn){
		bit[k] += val;
		k += k&-k;
	}
}
int sum(int k){
	int s = 0;
	while(k > 0){
		s += bit[k];
		k -= k&-k;
	}
	return s;
}
void solve(){
	int n;
	cin >> n;
	int a[n];
	vector<pii> v;
	fr(i, 0, n){
		cin >> a[i];
		v.pb({a[i], i});
	}
	sort(all(v));
	int val = 0;
	int pr = -1;
	for(auto u : v){
		if(u.st != pr) pr = u.st, ++val;
		a[u.nd] = val;
	}
	
	ll le[n];
	ll ri[n];
	fr(i, 0, n){
		le[i] = sum(a[i]-1);
		update(a[i], +1);
	}
	fr(i, 0, n) update(a[i],-1);
	for(int i = n-1; i >= 0; i --){
		ri[i] = sum(a[i]-1);
		update(a[i], +1);
	}
	ll ans = 0;
	fr(i, 0, n){
		ans += le[i]*ri[i];
	}
	cout<<ans<<endl;
	
	
}
 
int main(){
	ios_base::sync_with_stdio(false);
	cin.tie(NULL);
	solve();
}

• Subtask 1: 0 / 2
• Subtask 2: 4 / 4
• Subtask 3: 9 / 9
• Subtask 4: 0 / 36
• Subtask 5: 0 / 28
• Subtask 6: 9 / 9
• Subtask 7: 0 / 12