Submission #1267289

#	Time	Username	Problem	Language	Result	Execution time	Memory
1267289		nguyenvietanh	Mountains (NOI20_mountains)	C++20	100 / 100	373 ms	40500 KiB

Mountains

#include <bits/stdc++.h>
using namespace std;
#define int long long
#define fi first
#define se second
#define pii pair<int,int>
#define inp(name) freopen(name, "r", stdin);
#define out(name) freopen(name, "w", stdout);
const int N = 3e5 + 5;
const int mod = 998244353;
int n, cur = 0;
int a[N], ans[N], tree[N];
void update(int u, int v){
    while (u <= cur){
        tree[u] += v; u += (u & -u);
    }
}
int get(int u){
    int ans = 0;
    while (u > 0){
        ans += tree[u]; u -= (u & -u);
    }
    return ans;
}
signed main(){
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    cin >> n;
    set <int> s; map <int, int> m;
    for (int i = 1; i <= n; i ++){
        cin >> a[i]; s.insert(a[i]);
        ans[i] = 1;
    }
    for (auto i : s) m[i] = ++cur;
    for (int i = 1; i <= n; i ++) a[i] = m[a[i]];
    for (int i = 1; i <= n; i ++){
        ans[i] *= get(a[i] - 1);
        update(a[i], 1);
    }
    for (int i = 0; i <= cur; i ++) tree[i] = 0;
    int res = 0;
    for (int i = n; i >= 1; i --){
        ans[i] *= get(a[i] - 1);
        update(a[i], 1);
        res += ans[i];
    }
    cout<< res; 
}

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