제출 #19688

#	제출 시각	아이디	문제	언어	결과	실행 시간	메모리
19688		Namnamseo	괄호 (kriii4_R)	C++14	100 / 100	419 ms	32332 KiB

R

#include <cstdio>

typedef long long ll;
const ll M=int(1e9)+7;

ll catalan[1000010];
ll fact[2000010];
ll kpow[1000010];

ll pow(ll a,ll b){
    if(b==0) return 1;
    ll ret=pow(a,b/2);
    ret=(ret*ret)%M;
    if(b&1) ret=(ret*a)%M;
    return ret;
}

int main()
{
    int n,k;
    int i;
    scanf("%d%d",&n,&k);
    
    fact[0]=1;
    kpow[0]=1;
    for(i=1; i<=2*n; ++i) fact[i]=(fact[i-1]*i)%M;
    catalan[0]=1;
    for(i=1; i<=n; ++i){
        catalan[i] = fact[2*i] * pow( fact[i+1]*fact[i]%M, M-2 ) %M;
        kpow[i] = (kpow[i-1]*k)%M;
    }

    ll cur=1;
    
    for(i=1; i<=n; ++i){
        cur=cur*(k+1)%M;
        if(i%2 == 1){ // can perfectly match
            //printf("i %d; perfect match %I64d\n",i,catalan[(i-1)/2]*kpow[(i-1)/2]%M);
            cur -= catalan[(i-1)/2]*kpow[(i-1)/2]%M;
            cur = (cur+M)%M;
        }
        //printf("i %d : %I64d\n",i,cur);
    }
    printf("%d\n",int(cur));
    return 0;
}

• Subtask 1: 8 / 8
• Subtask 2: 92 / 92