#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using pi = pair<int, int>;
using pl = pair<ll, ll>;
using vi = vector<int>;
using vl = vector<ll>;
using vpi = vector<pi>;
using vpl = vector<pl>;
#define fur(i, a, b) for(ll i = a; i <= (ll)b; ++i)
#define ruf(i, a, b) for(ll i = a; i >= (ll)b; --i)
#define fr first
#define sc second
#define mp make_pair
#define pb push_back
#define nl "\n"
#define all(x) (x).begin(),(x).end()
#define rall(x) (x).rbegin(),(x).rend()
ll n;
ll lef[300000 + 1];
ll rig[300000 + 1];
ll rsum(ll pos) {
ll s = 0;
while(pos >= 1) {
s += rig[pos];
pos -= (pos & -pos);
}
return s;
}
void rupdate(ll pos, ll val) {
while(pos <= n) {
rig[pos] += val;
pos += (pos & -pos);
}
}
ll lsum(ll pos) {
ll s = 0;
while(pos >= 1) {
s += lef[pos];
pos -= (pos & -pos);
}
return s;
}
void lupdate(ll pos, ll val) {
while(pos <= n) {
lef[pos] += val;
pos += (pos & -pos);
}
}
void solve()
{
cin >> n;
pl h[n + 1];
fur(i, 1, n) {
cin >> h[i].fr;
h[i].sc = i;
}
sort(h + 1, h + n + 1, [&] (pl lef, pl rig) {
if(lef.fr != rig.fr)
return lef.fr < rig.fr;
return lef.sc > rig.sc;
});
/* fur(i, 1, n) */
/* cout << h[i].fr << ' ' << h[i].sc << nl; */
/* cout << nl; */
ll l[n + 1], r[n + 1];
fur(i, 1, n) {
l[h[i].sc] = lsum(h[i].sc);
lupdate(h[i].sc, 1);
}
/* fur(i, 1, n) */
/* cout << l[i] << ' '; */
/* cout << nl; */
fur(i, 1, n)
h[i].sc = n + 1 - h[i].sc;
sort(h + 1, h + n + 1, [&] (pl lef, pl rig) {
if(lef.fr != rig.fr)
return lef.fr < rig.fr;
return lef.sc > rig.sc;
});
/* fur(i, 1, n) */
/* cout << h[i].fr << ' ' << h[i].sc << nl; */
/* cout << nl; */
fur(i, 1, n) {
r[n + 1 - h[i].sc] = rsum(h[i].sc);
rupdate(h[i].sc, 1);
}
/* fur(i, 1, n) */
/* cout << r[i] << ' '; */
/* cout << nl; */
ll ans = 0;
fur(i, 1, n) {
ans += l[i] * r[i];
}
cout << ans << nl;
}
int main()
{
ios::sync_with_stdio(0);
cin.tie(0);
ll t = 1;
/* cin >> t; */
while(t--)
{
solve();
}
}
Compilation message
/usr/bin/ld: /tmp/ccecmywD.o: in function `main':
grader.cpp:(.text.startup+0x0): multiple definition of `main'; /tmp/ccv9Endz.o:mountains.cpp:(.text.startup+0x0): first defined here
/usr/bin/ld: /tmp/ccecmywD.o: in function `main':
grader.cpp:(.text.startup+0x238): undefined reference to `maximum_deevs(std::vector<int, std::allocator<int> >)'
collect2: error: ld returned 1 exit status
