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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
#654853#6137. Sub-cycle Graphucup-team5217#WA 130ms27252kbC++231.5kb2024-10-18 22:35:302024-10-18 22:35:31

Judging History

你现在查看的是最新测评结果

  • [2024-10-18 22:35:31]
  • 评测
  • 测评结果:WA
  • 用时:130ms
  • 内存:27252kb
  • [2024-10-18 22:35:30]
  • 提交

answer

#include <bits/stdc++.h>
#define ll long long

using namespace std;

const int N = 2e6 + 10;
const int mod = 1e9 + 7;
int fac[N], ifac[N], inv[N];

int C(int n, int m) {
    if (n < m || m < 0) return 0;
    return 1ll * fac[n] * ifac[m] % mod * ifac[n - m] % mod;
}

int add(int x, int y) {
    return x + y >= mod ? x + y - mod : x + y;
}

int qpow(int a, int b = mod - 2) {
    int res = 1;
    while (b) {
        if (b & 1) res = 1ll * res * a % mod;
        a = 1ll * a * a % mod;
        b >>= 1;
    }
    return res;
}

void solve() {
    ll n, m;
    scanf("%lld%lld", &n, &m);
    if (m >= n) {
        puts("0");
        return ;
    }
    int ans = 0;
    for (int i = 0; i <= n - m; ++i) {
        // ans = add(ans, 1ll * ifac[i - 2 * (n - m)] * C(i + (n - m) - 1, (n - m) - 1));
        ans = add(ans, 1ll * C(n - m, i) * C(m + i - 1, i - 1) % mod);
        // cerr << 1ll * 1ll * C(n - m, i) * C(m + i - 1, i - 1) % mod * fac[n] % mod * qpow(qpow(2), n - m) % mod << '\n';
    }
    ans = 1ll * ans * fac[n] % mod;
    ans = 1ll * ans * qpow(qpow(2), n - m) % mod;
    ans = 1ll * ans * ifac[n - m] % mod;
    printf("%d\n", ans);
}

int main() {
    fac[0] = fac[1] = inv[1] = ifac[0] = ifac[1] = 1;
    for (int i = 2; i <= 2000000; ++i) {
        fac[i] = 1ll * fac[i - 1] * i % mod;
        inv[i] = 1ll * (mod - mod / i) * inv[mod % i] % mod;
        ifac[i] = 1ll * ifac[i - 1] * inv[i] % mod;
    }
    int T;
    scanf("%d", &T);
    while (T--) {
        solve();
    }
    return 0;
}

详细

Test #1:

score: 100
Accepted
time: 16ms
memory: 27192kb

input:

3
4 2
4 3
5 3

output:

15
12
90

result:

ok 3 number(s): "15 12 90"

Test #2:

score: -100
Wrong Answer
time: 130ms
memory: 27252kb

input:

17446
3 0
3 1
3 2
3 3
4 0
4 1
4 2
4 3
4 4
5 0
5 1
5 2
5 3
5 4
5 5
6 0
6 1
6 2
6 3
6 4
6 5
6 6
7 0
7 1
7 2
7 3
7 4
7 5
7 6
7 7
8 0
8 1
8 2
8 3
8 4
8 5
8 6
8 7
8 8
9 0
9 1
9 2
9 3
9 4
9 5
9 6
9 7
9 8
9 9
10 0
10 1
10 2
10 3
10 4
10 5
10 6
10 7
10 8
10 9
10 10
11 0
11 1
11 2
11 3
11 4
11 5
11 6
11 7
11...

output:

875000007
3
3
0
437500004
6
15
12
0
718750006
10
45
90
60
0
859375007
15
105
375
630
360
0
429687504
21
210
1155
3465
5040
2520
0
714843756
28
378
2940
13545
35280
45360
20160
0
857421882
36
630
6552
42525
170100
393120
453600
181440
0
928710945
45
990
13230
114345
643545
2286900
4762800
4989600
181...

result:

wrong answer 1st numbers differ - expected: '1', found: '875000007'