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General

# Author Problem Lang Verdict Time Memory Sent Judged
86635067 Practice:
JKLover
961G - 14 GNU C++17 Accepted 187 ms 5220 KB 2020-07-12 11:59:54 2020-07-12 11:59:54

→ Source
//%std
#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
{
int out = 0, fh = 1;
char jp = getchar();
while ((jp > '9' || jp < '0') && jp != '-')
jp = getchar();
if (jp == '-')
fh = -1, jp = getchar();
while (jp >= '0' && jp <= '9')
out = out * 10 + jp - '0', jp = getchar();
return out * fh;
}
void print(int x)
{
if (x >= 10)
print(x / 10);
putchar('0' + x % 10);
}
void write(int x, char c)
{
if (x < 0)
putchar('-'), x = -x;
print(x);
putchar(c);
}
const int P = 1e9 + 7;
{
return a + b >= P ? a + b - P : a + b;
}
void inc(int &a, int b)
{
}
int mul(int a, int b)
{
return 1LL * a * b % P;
}
int fpow(int a, int b)
{
int res = 1;
while (b)
{
if (b & 1)
res = mul(res, a);
a = mul(a, a);
b >>= 1;
}
return res;
}
const int N = 2e5 + 10;
int fac[N], invfac[N];
int S(int n, int k)
{
if (n < k)
return 0;
int s = 0;
for (int i = 0; i <= k; ++i)
{
int t = mul(mul(invfac[k - i], invfac[i]), fpow(k - i, n));
if (i & 1)
inc(s, P - t);
else
inc(s, t);
}
return s;
}
int n, k, ans = 0;
int main()
{
fac[0] = 1;
for (int i = 1; i <= n; ++i)
inc(ans, read()), fac[i] = mul(fac[i - 1], i);
invfac[n] = fpow(fac[n], P - 2);
for (int i = n - 1; i >= 0; --i)
invfac[i] = mul(invfac[i + 1], i + 1);
int coef = add(mul(S(n - 1, k), n - 1), S(n, k));
ans = mul(ans, coef);
cout << ans << '\n';
return 0;
}


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Time: ? ms, memory: ? KB
Verdict: ?
Input
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Participant's output
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