Submission #1116714

#	Time	Username	Problem	Language	Result	Execution time	Memory
1116714		JanPham	Fancy Fence (CEOI20_fancyfence)	C++17	12 / 100	1 ms	2576 KiB

fancyfence

#include <bits/stdc++.h>

using namespace std;

#define pb push_back
#define fi first
#define se second
#define TranLeThanhTam "TranLeThanhTam"
#define all(v) v.begin(),v.end()
#define reset(a,i) memset(a,i,sizeof(a))
#define FOR(i,a,b) for (int i = (a), _b = (b); i <= _b; ++i)
#define FORD(i,a,b) for (int i = (a), _b = (b); i >= _b; --i)
#define compact(v) sort(all(v)), v.erase(unique(all(v)), end(v))
#define sz(v) (int) v.size()
#define MASK(i) (1LL << (i)
#define BIT(i,x) ((x & MASK(i)) >> (i))
#define int ll

typedef long long ll;
typedef long double lb;
typedef pair<ll,ll> pll;
typedef pair<int,int> pii;

const int Thanh_Tam = 1e5 + 17;
const int inf = 1e9 + 17;
const long long infll = 1e18 + 17;
const int MOD = 1e9 + 7;
const int Log = 18;
const int dx[4] = {-1, 0, 1, 0};
const int dy[4] = {0, 1, 0, -1};
const int max_block_size = 270;
const ll P = 311;
const int maxA = 1e2 + 17;
const int addi = 1e9;
const char dir[4] = {'W', 'S', 'N', 'E'};
const int Mod[3] = {998244353, MOD, 759186269};

ll mul(ll a, ll b, ll mod);
ll binpow(ll a, ll b, ll mod)
{
    ll res = 1;
    while (b > 0)
    {
        if (b & 1) res = mul(res,a,mod);
        b >>= 1;
        a = mul(a,a,mod);
    }
    return res;
}
ll add(ll a, ll b, ll mod) { return (a + b) % mod;                 }
ll sub(ll a, ll b, ll mod) { return (a - b + mod) % mod;          }
ll mul(ll a, ll b, ll mod) { return ((a % mod) * (b % mod)) % mod; }
ll div(ll a, ll b, ll mod) { return mul(a, binpow(b, mod - 2, mod), mod); }

mt19937 rng(chrono::high_resolution_clock::now().time_since_epoch().count());
ll rand_range(ll l, ll r) { return uniform_int_distribution<ll>(l,r)(rng); }

int n;
int h[Thanh_Tam], w[Thanh_Tam], l[Thanh_Tam], r[Thanh_Tam];
ll pref_w[Thanh_Tam];
ll ans = 0;
stack<int> st;
vector<pii> order;
map<pair<int,pii>, bool> mp;

ll sum(int x)
{
    return ((1LL * x * (x + 1)) >> 1) % MOD;
}

ll calc(int x, int y)
{
    return (1LL * sum(x) * sum(y)) % MOD;
}

ll merge(int x1, int y1, int x2, int y2)
{
    if (x1 != x2) return 0;
    return (sum(x1) * 1LL * y1 * y2) % MOD; 
}

void ThanhTam()
{
    cin >> n;
    FOR(i,1,n) cin >> h[i];
    FOR(i,1,n) cin >> w[i];

    //Prepare
    FOR(i,1,n) pref_w[i] = pref_w[i - 1] + w[i];
    
    //Find left
    while (!st.empty()) st.pop();
    FOR(i,1,n)
    {
        while (!st.empty()) 
            if (h[st.top()] >= h[i]) st.pop();
        else break;

        if (st.empty()) l[i] = 0;
        else l[i] = st.top();

        st.push(i);
    }

    //Find right
    while (!st.empty()) st.pop();
    FORD(i,n,1)
    {
        while (!st.empty()) 
            if (h[st.top()] >= h[i]) st.pop();
        else break;

        if (st.empty()) r[i] = n + 1;
        else r[i] = st.top();

        st.push(i);
    }


    //Calculate answer
    FOR(i,1,n)    
        if (!mp.count({h[i], {l[i], r[i]}})) 
        {
            ans = add(ans, calc(pref_w[r[i] - 1] - pref_w[l[i]], h[i] - min(h[i], max(h[l[i]], h[r[i]]))), MOD);
            mp[{h[i], {l[i], r[i]}}] = true;
            //cout << ans << ' ';
            ans = add(ans, merge(pref_w[r[i] - 1] - pref_w[l[i]], h[i] - min(h[i], max(h[l[i]], h[r[i]])), pref_w[r[i] - 1] - pref_w[l[i]], min(h[i], max(h[l[i]], h[r[i]]))), MOD);
            //cout << ans << '\n';
        }
    cout << ans;
    return;
}

signed main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    cout.tie(NULL);

    if (fopen(TranLeThanhTam".inp","r"))
    {
        freopen(TranLeThanhTam".inp","r",stdin);
        freopen(TranLeThanhTam".out","w",stdout);
    }

    int t = 1;
    //cin >> t;
    while (t--)
        ThanhTam();    

    return 0;
}

/*
2 * 4 => 30
2 * 2 => 9
2 * 3 => 18
2 * 1 => 3

Cách suy ra 2 * 4 từ 2 * 3 và 2 * 1
2 * 1 + 2 * 3 + 2 * 3 * 1 = 3 + 18 + 9 = 30 (Điều kiện: 2 cạnh đầu phải bằng nhau)

         0
      0000
  00000000
  00000000
0000000000
*/

Compilation message (stderr)

fancyfence.cpp: In function 'int main()':
fancyfence.cpp:142:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  142 |         freopen(TranLeThanhTam".inp","r",stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
fancyfence.cpp:143:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  143 |         freopen(TranLeThanhTam".out","w",stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 0 / 0
• Subtask 2: 12 / 12
• Subtask 3: 0 / 13
• Subtask 4: 0 / 15
• Subtask 5: 0 / 15
• Subtask 6: 0 / 18
• Subtask 7: 0 / 27