Ural 1172 Ship Routes

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大數什麼的果斷python 無壓力.....

Code:

dp=[]
def check(a,cur):
	for i in xrange(0,3) :
		if i!=cur:
			if a[i]!=0:
				return 0
	return 1

def dfs(a,cur):
	if dp[cur][a[0]][a[1]][a[2]]!=-1:
		return dp[cur][a[0]][a[1]][a[2]]
	if check(a,cur):
		if a[cur]==1 and cur!=0:
			dp[cur][a[0]][a[1]][a[2]] = 1
		else :
			dp[cur][a[0]][a[1]][a[2]] = 0
		return dp[cur][a[0]][a[1]][a[2]]
	dp[cur][a[0]][a[1]][a[2]]	 = 0
	for i in xrange(0,3):
		if i!=cur and a[i]:
			b=[]
			for j in xrange(0,3):
				b.append(a[j])
			b[cur]-=1;
			dp[cur][a[0]][a[1]][a[2]] += dfs(b,i)*b[i]
	return dp[cur][a[0]][a[1]][a[2]] 
n = int(raw_input())
for i in xrange(0,3):
	a=[]
	for j in xrange(0,1+n):
		c=[]
		for k in xrange(0,n+1):
			d=[]
			for z in xrange(0,n+1):
				d.append(-1)
			c.append(d)
		a.append(c)
	dp.append(a)
a=[]
for i in xrange(0,3):
	a.append(n)
ans = dfs(a,0)/2;
print ans