Submission #1197459

#	Time	Username	Problem	Language	Result	Execution time	Memory
1197459		nvc2k8	Fancy Fence (CEOI20_fancyfence)	C++20	100 / 100	16 ms	2632 KiB

fancyfence

#include <bits/stdc++.h>
#define TASK "kasjdkasd"
#define INT_LIM (int) 2147483647
#define LL_LIM (long long) 9223372036854775807
#define ll long long
#define pii pair<int,int>
#define endl '\n'
#define mp make_pair
#define pb push_back
#define fi first
#define se second
#define BIT(i,x) (((i)>>(x))&1)
#define FOR(i,a,b) for(int i = (a); i<=(b); i++)
#define FORD(i,a,b) for(int i = (a); i>=(b); i--)
using namespace std;
///------------------------------------------///
const int MOD = 1e9+7;
const int div2 = 500000004;
int pw(int x, int p)
{
    int ret = 1;
    while (p>0)
    {
        if (p&1) ret = 1LL*ret*x%MOD;
        x = 1LL*x*x%MOD;
        p>>=1;
    }
    return ret;
}

void add(int &x, const int &y)
{
    x+=y;
    if (x>=MOD) x-=MOD;
}

int n;
int h[100005], w[100005];
int pre[100005], nx[100005];
stack<int> st;

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

    FOR(i, 1, n)
    {
        while (!st.empty() && h[st.top()]>=h[i]) st.pop();
        if (st.empty()) pre[i] = 1;
        else pre[i] = st.top()+1;
        st.push(i);
    }
    while (!st.empty()) st.pop();

    FORD(i, n, 1)
    {
        while (!st.empty() && h[st.top()]>h[i]) st.pop();
        if (st.empty()) nx[i] = n;
        else nx[i] = st.top()-1;
        st.push(i);
    }
}

int ans = 0;
int pf[100005];

int sum(int x)
{
    return 1LL*x*(x+1)%MOD*div2%MOD;
}

void solve()
{
    FOR(i, 1, n)
    {
        pf[i] = w[i]; add(pf[i], pf[i-1]);
    }

    FOR(i, 1, n)
    {
        add(ans, 1LL*sum(h[i])*sum(w[i])%MOD);
        int tmp = 0;
        int L = 0, R = 0;
        if (pre[i]<i) L = (pf[i-1]-pf[pre[i]-1]+MOD)%MOD;
        if (nx[i]>i) R = (pf[nx[i]]-pf[i]+MOD)%MOD;
        add(tmp, 1LL*L*R%MOD);
        add(tmp, 1LL*w[i]*(L+R)%MOD);
        add(ans, 1LL*sum(h[i])*tmp%MOD);
    }

    cout << ans;
}

signed main()
{
    ///--------------------------///
    ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0);
    if (fopen(TASK".INP","r")!=NULL)
    {
        freopen(TASK".INP","r",stdin);
        freopen(TASK".OUT","w",stdout);
    }
    ///--------------------------///

    int NTEST = 1;
    //cin >> NTEST;

    while (NTEST--)
    {
        inp();
        solve();
    }

    return 0;
}

///------------------------------------------///

Compilation message (stderr)

fancyfence.cpp: In function 'int main()':
fancyfence.cpp:108:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  108 |         freopen(TASK".INP","r",stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~
fancyfence.cpp:109:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  109 |         freopen(TASK".OUT","w",stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~

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