Submission #1228519

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Source Code Expand

n, m = map(int,raw_input().split())
mod = 10 ** 9 + 7
dp=[[[0] * (n + 1) for _ in xrange(n + 1)] for _ in xrange(2)]
dp[0][1][1] = 1
for i in xrange(m):
    for j in xrange(n + 1):
        for k in xrange(n + 1):
            dp[(i+1)%2][j][k] = 0
    for j in xrange(1, n + 1):
        for k in xrange(1, j + 1):
            dp[(i+1)%2][min(j+1,n)][k] += dp[i%2][j][k] * (n - j) % mod
            dp[(i+1)%2][j][k] += dp[i%2][j][k] * (j - k) % mod
            dp[(i+1)%2][j][j] += dp[i%2][j][k] * k % mod
print dp[m%2][n][n] % mod

Submission Info

Judge Result