深度优先搜索DFS

python代码先附上，解析改天补上。

class DFS():    def __init__(self,n):        self.numlen=n        self.result=[0 for i in range(n)]        self.book=[0 for i in range(n)]    def dfs(self,s):        step=s-1        if step==self.numlen:            r=''            for i in range(self.numlen):                r+=str(self.result[i])            print(r)            return        for i in range(self.numlen):            if self.book[i]==0:                self.result[step]=i+1                self.book[i]=1                self.dfs(s+1)                self.book[i]=0                #print(i,self.book[i])        returndfs=DFS(4)dfs.dfs(1)