HappyLeetcode1 Reverse Words in a String

HappyLeetcode1:Reverse Words in a String

题目描述：

题目思考：

建立一个数组，每个数组存储一个单词。

将该数组倒序输出，每输出一个单词后，紧跟着输出一个空格。

题目解题代码

Python

class Solution:

# @param s, a string

# @return a string

def reverseWords(self, s):

slist=[]

slist=s.split()

for i in range(len(slist)/2):

slist[i],slist[len(slist)-1-i]=slist[len(slist)-1-i],slist[i]

return ' '.join(slist)

C++

class Solution {

public:

void reverseWords(string &s) {

if(s.empty())

return;

//remove heading and trailing spaces

int i = 0;

while(i<s.size() && s[i] == ' ')

i++;

if(i == s.size())

{

s = "";

return;

}

int j = s.size() - 1;

while(j>=0 && s[j] == ' ')

j--;

if(j == -1)

{

s = "";

return;

}

s = s.substr(i,j - i + 1);

size_t pos = 0;

vector<string> strs;

size_t begin = 0;

while(begin < s.size())

{

pos = s.find_first_of(' ',begin);

if(pos == begin)

{

begin++;

continue;

}

else if(pos != -1)

strs.push_back(s.substr(begin,pos - begin));

else //pos == -1, the end

{

strs.push_back(s.substr(begin,s.size() - 1 - begin + 1));

break;

}

begin = pos + 1;

}

string ans;

for(int i = strs.size() - 1; i > 0; i--)

{

ans += strs[i];

ans += " ";

}

ans += strs[0];

s = ans;

}

};

题后总结

' '.join(slist) 堪称列表转字符串的神表达。

官网答案

One simple approach is a two-pass solution: First pass to split the string by spaces into an array of words, then second pass to extract the words in reversed order.

We can do better in one-pass. While iterating the string in reverse order, we keep track of a word’s begin and end position. When we are at the beginning of a word, we append it.