Submission #757433

#	Time	Username	Problem	Language	Result	Execution time	Memory
757433		Sam_a17	Fancy Fence (CEOI20_fancyfence)	C++17	100 / 100	38 ms	7788 KiB

fancyfence

#define _CRT_SECURE_NO_WARNINGS
#include <bits/stdc++.h>
// #include <atcoder/all>
#include <cstdio>
using namespace std;
 
#ifndef ONLINE_JUDGE
#define dbg(x) cerr << #x <<" "; print(x); cerr << endl;
#else
#define dbg(x)
#endif
 
#define sz(x) (int((x).size()))
#define len(x) (int)x.length()
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
#define clr(x) (x).clear()
#define uniq(x) x.resize(unique(all(x)) - x.begin());
 
#define pb push_back
#define popf pop_front
#define popb pop_back
#define ld long double
#define ll long long
 
void print(long long t) {cerr << t;}
void print(int t) {cerr << t;}
void print(string t) {cerr << t;}
void print(char t) {cerr << t;}
void print(double t) {cerr << t;}
void print(unsigned long long t) {cerr << t;}
void print(long double t) {cerr << t;}
 
template <class T, class V> void print(pair <T, V> p);
template <class T> void print(vector <T> v);
template <class T> void print(set <T> v);
template <class T, class V> void print(map <T, V> v);
template <class T> void print(multiset <T> v);
template <class T> void print(T v[],T n) {cerr << "["; for(int i = 0; i < n; i++) {cerr << v[i] << " ";} cerr << "]";}
template <class T, class V> void print(pair <T, V> p) {cerr << "{"; print(p.first); cerr << ","; print(p.second); cerr << "}";}
template <class T> void print(vector <T> v) {cerr << "[ "; for (T i : v) {print(i); cerr << " ";} cerr << "]";}
template <class T> void print(deque <T> v) {cerr << "[ "; for (T i : v) {print(i); cerr << " ";} cerr << "]";}
template <class T> void print(set <T> v) {cerr << "[ "; for (T i : v) {print(i); cerr << " ";} cerr << "]";}
template <class T> void print(multiset <T> v) {cerr << "[ "; for (T i : v) {print(i); cerr << " ";} cerr << "]";}
template <class T, class V> void print(map <T, V> v) {cerr << "[ "; for (auto i : v) {print(i); cerr << " ";} cerr << "]";}
 
#include <ext/pb_ds/assoc_container.hpp>
using namespace __gnu_pbds;
#define nl '\n'
 
// for random generations
mt19937 myrand(chrono::steady_clock::now().time_since_epoch().count());
// mt19937 myrand(131);
 
// for grid problems
int dx[8] = {-1,0,1,0,1,-1,1,-1};
int dy[8] = {0,1,0,-1,1,1,-1,-1};
 
long long ka() {
	long long x = 0;
	bool z = false;
	while (1)
	{
		char y = getchar();
		if (y == '-')
			z = true;
		else if ('0' <= y && y <= '9')
			x = x * 10 + y - '0';
		else
		{
			if (z)
				x *= -1;
			return x;
		}
	}
}
 
// lowest / (1 << 17) >= 1e5 / (1 << 18) >= 2e5 / (1 << 21) >= 1e6
void fastIO() {
  ios_base::sync_with_stdio(false);
  cin.tie(nullptr); cout.tie(nullptr);
}
// file in/out
void setIO(string str = "") {
  fastIO();
 
  if (str != "") {
    freopen((str + ".in").c_str(), "r", stdin);
    freopen((str + ".out").c_str(), "w", stdout);
  } else if(str == "input") {
    freopen("input.txt", "r", stdin);
    freopen("output.txt", "w", stdout);
  }
}
 
// Indexed Set
template <class T> using Tree = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
const long long mod = 1e9 + 7;
int n;
 
long long add(long long a, long long b) {
  return (a + b) % mod;
}
 
long long mult(long long a, long long b) {
  return (a * b) % mod;
}
 
long long sub(long long a, long long b) {
  return (a - b + 2 * mod) % mod;
}
 
long long pi(long long p) {
  long long ss = p * (p + 1) / 2;
  ss %= mod;
  return ss;
}
 
long long get(long long x, long long y) {
  x %= mod, y %= mod;
  return mult(pi(x), pi(y));
}
 
void solve_() {
  cin >> n;
 
  vector<long long> h(n + 1), w(n + 1), pref(n + 3);
 
  for(int i = 1; i <= n; i++) {
    cin >> h[i];
  }
 
  long long si = 0;
  for(int i = 1; i <= n; i++) {
    cin >> w[i];
    pref[i] = add(pref[i - 1], w[i]); 
    si = add(si, w[i]);
  }
 
  pref[n + 1] = pref[n];
 
  int ok = 1;
  for(int i = 2; i <= n; i++) {
    if(h[i] != h[i - 1]) {
      ok = 0;
    }
  }
 
  if(ok) {
    cout << get(si, h[1]) << '\n';
  } else {
 
    stack<pair<long long, long long>> st;
 
    vector<long long> left_lower(n + 1, 0);
    vector<long long> right_lower_or_eq(n + 1, n + 1);
 
    for(int i = 1; i <= n; i++) {
      while (!st.empty() && st.top().first >= h[i]) {
        right_lower_or_eq[st.top().second] = i;
        st.pop();
      }
 
      if(!st.empty()) {
        left_lower[i] = st.top().second;
      }
      st.push({h[i], i});      
    }
 
    long long ans = 0;
    for(int i = 1; i <= n; i++) {
      long long le = 0, re = 0;
 
      int itr = right_lower_or_eq[i] - 1;
      re = sub(pref[itr], pref[i]);
 
      int itl = left_lower[i];
      le = sub(pref[i - 1], pref[itl]);
 
      long long wi = add(le, re);
      wi = add(wi, w[i]);
 
      //
      long long pt = get(h[i], wi);
      pt = sub(pt, get(h[i], re));
      pt = sub(pt, get(h[i], le));
      ans = add(ans, pt);
    }
 
    cout << ans << '\n';
  }
}
 
int main() {
  setIO();
 
  auto solve = [&](int test_case)-> void {
    while(test_case--) {
      solve_();
    }
  };
 
  int test_cases = 1; 
  // cin >> test_cases;
  solve(test_cases);
 
  return 0;
}

Compilation message (stderr)

fancyfence.cpp: In function 'void setIO(std::string)':
fancyfence.cpp:88:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   88 |     freopen((str + ".in").c_str(), "r", stdin);
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
fancyfence.cpp:89:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   89 |     freopen((str + ".out").c_str(), "w", stdout);
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
fancyfence.cpp:91:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   91 |     freopen("input.txt", "r", stdin);
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~
fancyfence.cpp:92:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   92 |     freopen("output.txt", "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