Submission #981958

#	Time	Username	Problem	Language	Result	Execution time	Memory
981958		duckindog	Fancy Fence (CEOI20_fancyfence)	C++17	30 / 100	21 ms	4444 KiB

fancyfence

#include <bits/stdc++.h>

using namespace std;

const int N = 100'000 + 10,
          M = 1'000'000'007;
int n;
int h[N], w[N];
int d[N];

int fl[N], fr[N];

int32_t main() { 
  cin.tie(0)->sync_with_stdio(0);

  cin >> n;
  for (int i = 1; i <= n; ++i) cin >> h[i];
  for (int i = 1; i <= n; ++i) cin >> w[i];
  
  for (int i = 1; i <= n; ++i) d[i] = (d[i - 1] + w[i]) % M;
  
  {
    stack<int> st; st.push(0);
    for (int i = 1; i <= n; ++i) { 
      while (st.size() && h[st.top()] >= h[i]) st.pop();
      fl[i] = st.top() + 1;
      st.push(i);
    }
  }
  {  
    stack<int> st; st.push(n + 1);
    for (int i = n; i >= 1; --i) { 
      while (st.size() && h[st.top()] >= h[i]) st.pop();
      fr[i] = st.top() - 1;
      st.push(i);
    }
  }

  auto cal = [&](int l, int r) { return 1ll * (l + r) * (r - l + 1) / 2 % M; };
  auto add = [&](auto& x, long long val) { x = (x + val) % M; };
  auto sub = [&](auto& x, long long val) { x = ((x - val) % M + M) % M; };

  int answer = 0;
  for (int i = 1; i <= n; ++i) { 
    if (fl[i] == fl[i - 1] && fr[i] == fr[i - 1] && h[i] == h[i - 1]) continue;
    int l = fl[i], r = fr[i];
    int height = max(h[l - 1], h[r + 1]);
    add(answer, cal(1, d[r] - d[l - 1]) * cal(height + 1, h[i]));
  }

  cout << answer << "\n";
}

Compilation message (stderr)

fancyfence.cpp: In function 'int32_t main()':
fancyfence.cpp:41:8: warning: variable 'sub' set but not used [-Wunused-but-set-variable]
   41 |   auto sub = [&](auto& x, long long val) { x = ((x - val) % M + M) % M; };
      |        ^~~

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