Submission #1323681

#	Time	Username	Problem	Language	Result	Execution time	Memory
1323681		ziad3ssam10	캥거루 (CEOI16_kangaroo)	C++20	100 / 100	57 ms	32476 KiB

kangaroo

#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>

using namespace std;
using namespace __gnu_pbds;
template<typename T>
using orderedset = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
#define int long long
#define ll long long
#define ld long double
#define endl '\n'
#define wady                      \
    ios_base::sync_with_stdio(0); \
    cin.tie(0);                   \
    cout.tie(0);

void files() {
#ifndef ONLINE_JUDGE
    freopen("in.txt", "r", stdin);
    freopen("out.txt", "w", stdout);
#endif
}

const int mod = 1e9 + 7;
int add(int a,int b) {
    return (a + b) % mod;
}

int mul(int a,int b) {
    return (a * b) % mod;
}

const int N = 2000 + 20;
int n;
int dp[N][N];
int st, en;

int rec(int idx,int comp) {
    if (idx > n)return comp == 1;
    int &ret = dp[idx][comp];
    if (~ret)return ret;
    ret = 0;
    if (idx == st or idx == en) {
        ret = add(rec(idx + 1, comp + 1), ret);
        if (comp) ret = add(ret, rec(idx + 1, comp));
    } else {
        ret = add(ret, mul(rec(idx + 1, comp + 1), (comp + 1) - (idx > st) - (idx > en)));
        if (comp >= 2)ret = add(ret, mul(rec(idx + 1, comp - 1), comp - 1));
    }
    return ret;
}

void solve(int tc) {
    cin >> n;
    cin >> st >> en;
    memset(dp, -1, sizeof dp);
    cout << rec(1, 0) << endl;
}


signed main() {
    wady
  //  files();
    int t = 1;
   // cin >> t;
    int tc = 1;
    while (t--)
        solve(tc++);
}

Compilation message (stderr)

kangaroo.cpp: In function 'void files()':
kangaroo.cpp:20:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   20 |     freopen("in.txt", "r", stdin);
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~
kangaroo.cpp:21:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   21 |     freopen("out.txt", "w", stdout);
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 6 / 6
• Subtask 2: 30 / 30
• Subtask 3: 15 / 15
• Subtask 4: 49 / 49