P2915 [USACO08NOV]Mixed Up Cows G
下一个选择的数之和当前的数有关，状压DP即可。
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| #include <cstdio>
#include <algorithm>
using namespace std;
template <class Type>
void read(Type &x)
{
char c;
bool flag = false;
while ((c = getchar()) < '0' || c > '9')
c == '-' && (flag = true);
x = c - '0';
while ((c = getchar()) >= '0' && c <= '9')
x = (x << 3) + (x << 1) + c - '0';
flag && (x = ~x + 1);
}
template <class Type>
void write(Type x)
{
x < 0 && (putchar('-'), x = ~x + 1);
x > 9 && (write(x / 10), 0);
putchar(x % 10 + '0');
}
typedef long long LL;
const int N = 16, M = 1 << N;
LL f[N][M];
int n, m, w[N];
int main ()
{
read(n), read(m);
for (int i = 0; i < n; i++)
read(w[i]), w[i]--;
for (int i = 0; i < n; i++)
f[i][1 << i] = 1;
for (int i = 0; i < 1 << n; i++)
for (int j = 0; j < n; j++)
for (int k = 0; k < n; k++)
if (abs(w[j] - w[k]) > m && !(i >> k & 1))
f[k][i | 1 << k] += f[j][i];
LL res = 0;
for (int i = 0; i < n; i++)
res += f[i][(1 << n) - 1];
write(res);
return 0;
}
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