Submission #530885

#	Time	Username	Problem	Language	Result	Execution time	Memory
530885		cpp219	Asceticism (JOI18_asceticism)	C++17	100 / 100	23 ms	1104 KiB

asceticism

#include<bits/stdc++.h>
#define ll long long
#define ld long double
#define fs first
#define sc second
#define debug(y) cout<<y,exit(0)
using namespace std;
typedef pair<ll,ll> LL;
const ll N = 1e5 + 9;
const ll mod = 1e9 + 7;
const ll base = 31;

ll n,k,fac[N],ans,sum;

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

ll C(ll k,ll n){
    ll ts = fac[n],ms = fac[k] * fac[n - k]; ms %= mod;
    return (ts * bpow(ms,mod - 2))%mod;
}

int main(){
    ios_base::sync_with_stdio(NULL); cin.tie(0); cout.tie(0);
    #define task "tst"
    if (fopen(task".inp","r")){
        freopen(task".inp","r",stdin);
        //freopen(task".out","w",stdout);
    }
    cin>>n>>k; fac[0] = 1;
    for (ll i = 1;i < N;i++) fac[i] = (fac[i - 1] * i)%mod; //debug(C(2,4));
    for (ll i = 0;i <= k;i++){
        sum = (bpow(k - i,n) * C(i, n+1)) % mod; //debug(C(i,n + 1));
        if(i&1) ans = (ans -  sum + mod) % mod;
        else ans = (ans + sum) % mod;
    }
    debug(ans);
}

/* stuff you should look for
	* int overflow, array bounds
	* special cases (n=1?)
	* do smth instead of nothing and stay organized
	* WRITE STUFF DOWN
	* DON'T GET STUCK ON ONE APPROACH
*/

Compilation message (stderr)

asceticism.cpp: In function 'int main()':
asceticism.cpp:33:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   33 |         freopen(task".inp","r",stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 4 / 4
• Subtask 2: 20 / 20
• Subtask 3: 25 / 25
• Subtask 4: 51 / 51