Submission #21289

#	Time	Username	Problem	Language	Result	Execution time	Memory
21289		suzy	괄호 (kriii4_R)	C++11	100 / 100	483 ms	16740 KiB

R

#include <stdio.h>

#define MOD 1000000007LL

typedef long long lli;

lli d[1000001], c[1000001];

lli pw(lli n, lli x) {
	if(x==0) return 1;
	if(x%2) return n*pw(n,x-1)%MOD;
	else { lli ret=pw(n,x/2); return ret*ret%MOD; }
}

int main() {
	c[1]=1;
	for(lli i=2;i<=1000000;i++) {
		lli aa=(2*i-1)*(2*i)%MOD;
		lli bb=pw(i*(i+1)%MOD,MOD-2);
		c[i]=c[i-1]*aa%MOD*bb%MOD;
	}
	lli n, k;
	scanf("%lld %lld",&n,&k);
	d[1]=k;
	for(lli i=2;i<=n;i++) {
		if(i%2) d[i]=(d[i-1]*(k+1)%MOD-c[(i-1)/2]*pw(k,(i-1)/2)%MOD+MOD)%MOD;
		else d[i]=d[i-1]*(k+1)%MOD;
	}
	printf("%lld\n",d[n]);
	return 0;
}

Compilation message (stderr)

R.cpp: In function 'int main()':
R.cpp:23:26: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%lld %lld",&n,&k);
                          ^

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