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IDProblemSubmitterResultTimeMemoryLanguageFile sizeSubmit timeJudge time
#164760#2908. countchen_0310015ms2752kbC++11731b2022-11-05 18:06:212022-11-05 18:06:23

answer

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const int p=1000000007,N=200000;
int T,n,m,fac[N+5],inv[N+5];
inline int qpow(int a,int b){
	int res=1;
	while(b){
		if(b&1)res=(ll)res*a%p;
		b>>=1,a=(ll)a*a%p;
	}
	return res;
}
inline int C(int n,int m){
	if(n<m || m<0)return 0;
	return (ll)fac[n]*inv[m]%p*inv[n-m]%p;
}
inline int solve(int n,int m){
	return n*(n+1ll)/2%p*C(n+m,m-1)%p;
}
int main(){
	scanf("%d",&T),fac[0]=1;
	for(int i=1;i<=N;++i)
		fac[i]=(ll)fac[i-1]*i%p;
	inv[N]=qpow(fac[N],p-2);
	for(int i=N;i>=1;--i)
		inv[i-1]=(ll)inv[i]*i%p;
	while(T--){
		scanf("%d%d",&n,&m),--n,--m;
		printf("%lld\n",((ll)C(n+m,m)*(n+m)+solve(n,m)+solve(m,n))%p);
	}
	return 0;
}

Details

小提示:点击横条可展开更详细的信息

Test #1:

score: 20
Accepted
time: 3ms
memory: 2752kb

input:

10
1 1
2000 1997
117 1647
392 452
959 1883
1046 1627
1398 1124
1372 306
1799 1007
111 1765

output:

0
57631948
737963048
807538931
137760374
398194748
77480423
174938019
583393917
445670336

result:

ok 10 lines

Test #2:

score: 20
Accepted
time: 3ms
memory: 2752kb

input:

10
1 1
2000 1997
1218 1479
350 1244
784 1715
999 92
396 1393
1726 1511
624 756
900 317

output:

0
57631948
610566455
356523655
593949258
665757514
349394180
73375269
50652564
663822508

result:

ok 10 lines

Test #3:

score: 20
Accepted
time: 3ms
memory: 2748kb

input:

10
1 1
100000 99997
36934 50467
5497 37576
83775 15544
23817 68917
33052 49207
59924 39340
2708 2614...

output:

0
73866797
788834869
539491921
582239610
497376436
343937059
324406513
13225836
35059446

result:

ok 10 lines

Test #4:

score: 20
Accepted
time: 3ms
memory: 2752kb

input:

10
1 1
100000 99997
6792 14252
90281 65716
46434 67120
18977 30384
16191 33996
3425 10433
31783 4263...

output:

0
73866797
609230597
213203975
638117274
527713366
525065128
867713025
174019248
375031322

result:

ok 10 lines

Test #5:

score: 20
Accepted
time: 3ms
memory: 2752kb

input:

10
1 1
100000 99994
47270 99792
93093 92620
88764 20724
48143 99711
33293 89038
2816 16811
97638 670...

output:

0
796648553
5720713
279796657
802039459
22848874
23038351
610731858
629891152
812026839

result:

ok 10 lines