提交时间:2022-10-17 13:40:05

运行 ID: 60815

#include<bits/stdc++.h> using namespace std; const int N = 5e5 + 10; typedef long long ll; const int mod = 1e9 + 7; int n, a[N]; map<int,int>mp; int l[N], r[N]; int main() { cin >> n; for(int i = 1; i <= n; ++i) { cin >> a[i]; mp[a[i]] = 1; } mp.clear(); for(int i = 1; i <= n; ++i) { l[i] = mp[a[i]] + 1; mp[a[i]] = i; } mp.clear(); for(int i = n; i; --i) { if(!mp.count(a[i])) { r[i] = n; } else r[i] = mp[a[i]] - 1; mp[a[i]] = i; } ll ans = 0; for(int i = 1; i <= n; ++i) { ans += 1ll * a[i] * (i - l[i] + 1) % mod * (n - i + 1) % mod; ans %= mod; } cout << ans << endl; }