Given an input string, reverse the string word by word.
For example,
Given s = "the sky is blue
",
return "blue is sky the
".
Update (2015-02-12):
For C programmers: Try to solve it in-place in O(1) space.
click to show clarification.
Clarification:
- What constitutes a word?
A sequence of non-space characters constitutes a word. - Could the input string contain leading or trailing spaces?
Yes. However, your reversed string should not contain leading or trailing spaces. - How about multiple spaces between two words?
Reduce them to a single space in the reversed string.
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注意,
1,被空格包围的是单词
2,输入字符串可以以空格开头或结尾,但是结果中的字符不能以空格开头或结尾
3,输出字符串中单词间的空格是一个,不能重复出现空格.
思路:
对输入字符串进行去重空格操作,
对字符串中的每个单词进行反转
对整个字符串进行反转
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code
class Solution { public: void help_reverse(string &s,int start,int end){ while(start<end){///经典的反转字符串方法 swap(s[start++],s[end--]); } } string removeDuplicateSpace(string s){ string res; int b = 0; for(;b<(int)s.size();b++){ if(s[b]!= ‘ ‘){ break; } }/// int e = s.size() - 1; for(;e>=0;e--){ if(s[e]!=‘ ‘){ break; } } bool is_space = false; for(int i = b;i<=e;i++){ if(s[i] == ‘ ‘){ if(!is_space) is_space = true; else continue; }else{ is_space = false; } res.push_back(s[i]); } return res; } void reverseWords(string &s) { if(s.empty()) return; s = removeDuplicateSpace(s); int start = 0; for(size_t i = 0;i<s.size();i++){ if(s[i]!=‘ ‘){ start = i; }else{ continue; } size_t j = i; while(j<s.size() && s[j]!=‘ ‘){ j++; } j--; help_reverse(s,start,j); i = j++; } help_reverse(s,0,(int)s.size()-1); } };
时间: 2024-10-12 23:28:16