[leetcode]Scramble String @ Python

python

原题地址:https://oj.leetcode.com/problems/scramble-string/

题意:

Given a string s1, we may represent it as a binary tree by partitioning it to two non-empty substrings recursively.

Below is one possible representation of s1 = "great":

    great

/ \

gr eat

/ \ / \

g r e at

/ \

a t

To scramble the string, we may choose any non-leaf node and swap its two children.

For example, if we choose the node "gr" and swap its two children, it produces a scrambled string "rgeat".

    rgeat

/ \

rg eat

/ \ / \

r g e at

/ \

a t

We say that "rgeat" is a scrambled string of "great".

Similarly, if we continue to swap the children of nodes "eat" and "at", it produces a scrambled string "rgtae".

    rgtae

/ \

rg tae

/ \ / \

r g ta e

/ \

t a

We say that "rgtae" is a scrambled string of "great".

Given two strings s1 and s2 of the same length, determine if s2 is a scrambled string of s1.

解题思路:二叉树的问题一般使用递归来解决。

代码:

class Solution:

# @return a boolean

def isScramble(self, s1, s2):

if len(s1)!=len(s2): return False

if s1==s2: return True

l1=list(s1); l2=list(s2)

l1.sort();l2.sort()

if l1!=l2: return False

length=len(s1)

for i in range(1,length):

if self.isScramble(s1[:i],s2[:i]) and self.isScramble(s1[i:],s2[i:]): return True

if self.isScramble(s1[:i],s2[length-i:]) and self.isScramble(s1[i:],s2[:length-i]): return True

return False

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