CF1064Div2 C

贪心模拟即可
记录前后，删除前ans+max(vall,valr)并更新l

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void solve() {
    int n;cin >> n;
    set<pii>st;
    map<int, int>mp;
    vector<int>bef(n + 1), aft(n + 1);
    for (int i = 1;i <= n;i++) {
        bef[i] = (i == 1 ? n : i - 1);
        aft[i] = (i == n ? 1 : i + 1);
        int x;cin >> x;st.insert({ x,i });
        mp[i] = x;
    }
    i64 ans = 0;
    while (st.size() > 1) {
        auto [x, i] = *st.begin();
        int lr = min(mp[bef[i]], mp[aft[i]]);
        ans += lr;
        aft[bef[i]] = aft[i];
        bef[aft[i]] = bef[i];
        st.erase(st.begin());
    }
    cout << ans << endl;
}