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大数什么的果断python 无压力.....

Code:

dp=[]def check(a,cur):for i in xrange(0,3) :if i!=cur:if a[i]!=0:return 0return 1def 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]] = 1else :dp[cur][a[0]][a[1]][a[2]] = 0return dp[cur][a[0]][a[1]][a[2]]dp[cur][a[0]][a[1]][a[2]] = 0for 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