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ID题目提交者结果用时内存语言文件大小提交时间测评时间
#166226#2908. countzsjhhh10042ms4320kbC++11805b2022-11-17 11:22:392022-11-17 11:22:41

answer

#include<bits/stdc++.h>
#define int long long
using namespace std;
const int mod = 1e9 + 7;
const int maxn = 2e5 + 5;
int inv[maxn];
int sum[maxn];
int get_ans(int n,int m) {
    int ans = (n * m - 1) % mod;
    ans = ans * (inv[m - 1] * (sum[n + m - 2] * inv[n - 1] % mod) % mod) % mod;
    return ans;
}
signed main() {
    int t;
    cin>>t;
    inv[0] = 1;
    inv[1] = 1;
    sum[1] = 1;
    sum[0] = 1;
    for(int i = 2;i <= 2e5;i++) {
        sum[i] = sum[i - 1] * i % mod;
    }
    for(int i = 2;i <= 2e5;i++) {
        inv[i] = (mod - mod / i) * inv[mod % i] % mod;
    }
    for(int i = 2;i <= 2e5;i++) {
        inv[i] = inv[i] * inv[i - 1] % mod;
    }
    int n,m;
    while(t--) {
        cin>>n>>m;
        cout<<get_ans(n,m)<<endl;
    }
    return 0;
}

详细

小提示:点击横条可展开更详细的信息

Test #1:

score: 20
Accepted
time: 5ms
memory: 4316kb

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: 9ms
memory: 4320kb

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: 9ms
memory: 4320kb

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: 9ms
memory: 4320kb

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: 10ms
memory: 4320kb

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