Submission #1329713

#	Time	Username	Problem	Language	Result	Execution time	Memory
1329713		nguyenkhanghuy	Fancy Fence (CEOI20_fancyfence)	C++20	0 / 100	1 ms	344 KiB

fancyfence

#include <bits/stdc++.h>
using namespace std;

// JUST ME BRO
// TRY OLP

#define ll int64_t
#define FOR(I, L, R) for(int I(L) ; I <= (int)(R) ; ++I)
#define FOD(I, R, L) for(int I(R) ; I >= (int)(L) ; --I)
#define FOA(I, A) for(auto &I : A)
#define fi first
#define se second

const ll mod = 1e9+7;
const ll N = 2e5 + 5;

ll n;
ll H[N], W[N], suf[N], sum;

ll power(ll a, ll b){
    ll res = 1;
    a %= mod;
    while(b){
        if(b & 1) res = res * a % mod;
        a = a * a % mod;
        b >>= 1;
    }
    return res;
}

void sub1 () {

    ll inv2 = power(2, mod - 2);

    ll x = H[1] % mod;
    ll s = sum % mod;

    ll a = x * ((x + 1) % mod) % mod * inv2 % mod;
    ll b = s * ((s + 1) % mod) % mod * inv2 % mod;

    cout << a * b % mod;
}

void sub2() {

    suf[n+1] = 0;

    FOD(i , n , 1){
        suf[i] = (suf[i+1] + W[i]) % mod;
    }

    ll ans = 0;
    ll inv2 = (mod + 1) / 2;

    FOR(i , 1 , n){

        ll ww = suf[i];

        ll ways = ww % mod * ((ww + 1) % mod) % mod;
        ways = ways * inv2 % mod;

        ans = (ans + H[i] % mod * ways % mod) % mod;
    }

    cout << ans % mod;
}

signed main() {

    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);

    freopen("FENCE.INP" , "r" , stdin);
    freopen("FENCE.OUT" , "w" , stdout);

    cin >> n ;

    bool check = false;
    bool check2 = false;

    FOR (i , 1 , n ) {
        cin >> H[i];

        if (i > 1 ) {

            if ( H[i] != H[i-1])
                check = true;

            if ( H[i-1] > H[i])
                check2 = true;
        }
    }

    FOR (i , 1 , n ) {
        cin >> W[i];
        sum += W[i];
    }

    if (check == false)
        sub1();
    else
        sub2();

}

Compilation message (stderr)

fancyfence.cpp: In function 'int main()':
fancyfence.cpp:74:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   74 |     freopen("FENCE.INP" , "r" , stdin);
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~
fancyfence.cpp:75:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   75 |     freopen("FENCE.OUT" , "w" , stdout);
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~

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