Submission #21295

#	Submission time	Handle	Problem	Language	Result	Execution time	Memory
21295	2017-04-12T14:24:42 Z	suzy	순열 (kriii4_T)	C++14	100 / 100	369 ms	8928 KB

T

#include <stdio.h>

#define MOD 1000000007

typedef long long lli;

lli fac[1000002];
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() {
	lli n, k;
	fac[0]=1;
	for(lli i=1;i<=1000001;i++)
		fac[i]=fac[i-1]*i%MOD;
	scanf("%lld %lld",&n,&k); k++;
	if(k>n) {
		puts("0"); return 0;
	}
	lli res=0, ncl=fac[n+1]*pw(fac[n-k],MOD-2)%MOD*pw(fac[k+1],MOD-2)%MOD;
	for(lli l=k;l<=n;l++) {
		res+=(n-l+1)*fac[l]%MOD*fac[n-l]%MOD*ncl%MOD;
		res%=MOD;
		ncl=ncl*(n-l)%MOD*pw(l+2,MOD-2)%MOD;
	}
	printf("%lld\n",res);
	return 0;
}

Compilation message

T.cpp: In function 'int main()':
T.cpp:19:26: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%lld %lld",&n,&k); k++;
                          ^

Subtask #1

8.0 / 8.0

#	Verdict	Execution time	Memory	Grader output
1	Correct	6 ms	8928 KB	Output is correct
2	Correct	6 ms	8928 KB	Output is correct
3	Correct	3 ms	8928 KB	Output is correct
4	Correct	6 ms	8928 KB	Output is correct
5	Correct	6 ms	8928 KB	Output is correct
6	Correct	9 ms	8928 KB	Output is correct
7	Correct	9 ms	8928 KB	Output is correct
8	Correct	6 ms	8928 KB	Output is correct
9	Correct	3 ms	8928 KB	Output is correct
10	Correct	9 ms	8928 KB	Output is correct
11	Correct	0 ms	8928 KB	Output is correct
12	Correct	6 ms	8928 KB	Output is correct
13	Correct	3 ms	8928 KB	Output is correct
14	Correct	3 ms	8928 KB	Output is correct
15	Correct	6 ms	8928 KB	Output is correct
16	Correct	3 ms	8928 KB	Output is correct
17	Correct	3 ms	8928 KB	Output is correct
18	Correct	3 ms	8928 KB	Output is correct
19	Correct	6 ms	8928 KB	Output is correct
20	Correct	9 ms	8928 KB	Output is correct
21	Correct	9 ms	8928 KB	Output is correct
22	Correct	9 ms	8928 KB	Output is correct
23	Correct	6 ms	8928 KB	Output is correct
24	Correct	6 ms	8928 KB	Output is correct
25	Correct	6 ms	8928 KB	Output is correct
26	Correct	9 ms	8928 KB	Output is correct
27	Correct	9 ms	8928 KB	Output is correct
28	Correct	9 ms	8928 KB	Output is correct
29	Correct	9 ms	8928 KB	Output is correct
30	Correct	6 ms	8928 KB	Output is correct

Subtask #2

92.0 / 92.0

#	Verdict	Execution time	Memory	Grader output
1	Correct	316 ms	8928 KB	Output is correct
2	Correct	109 ms	8928 KB	Output is correct
3	Correct	53 ms	8928 KB	Output is correct
4	Correct	33 ms	8928 KB	Output is correct
5	Correct	43 ms	8928 KB	Output is correct
6	Correct	29 ms	8928 KB	Output is correct
7	Correct	253 ms	8928 KB	Output is correct
8	Correct	156 ms	8928 KB	Output is correct
9	Correct	56 ms	8928 KB	Output is correct
10	Correct	13 ms	8928 KB	Output is correct
11	Correct	113 ms	8928 KB	Output is correct
12	Correct	9 ms	8928 KB	Output is correct
13	Correct	56 ms	8928 KB	Output is correct
14	Correct	226 ms	8928 KB	Output is correct
15	Correct	143 ms	8928 KB	Output is correct
16	Correct	243 ms	8928 KB	Output is correct
17	Correct	99 ms	8928 KB	Output is correct
18	Correct	89 ms	8928 KB	Output is correct
19	Correct	23 ms	8928 KB	Output is correct
20	Correct	123 ms	8928 KB	Output is correct
21	Correct	83 ms	8928 KB	Output is correct
22	Correct	193 ms	8928 KB	Output is correct
23	Correct	79 ms	8928 KB	Output is correct
24	Correct	43 ms	8928 KB	Output is correct
25	Correct	43 ms	8928 KB	Output is correct
26	Correct	143 ms	8928 KB	Output is correct
27	Correct	16 ms	8928 KB	Output is correct
28	Correct	0 ms	8928 KB	Output is correct
29	Correct	366 ms	8928 KB	Output is correct
30	Correct	369 ms	8928 KB	Output is correct