Reverse Words in a String

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最新推荐文章于 2024-01-04 11:20:32 发布

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分类专栏： LeetCode

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本文介绍了一种用于逆序字符串中单词的算法，并提供了详细的实现步骤。该算法首先整体逆序字符串，然后逐个逆序每个单词，确保结果中单词顺序反转且只保留单词间的单个空格。

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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.

做着题时一定要点开click to show clarification部分，不然会不知道哪错了

void reverseWord(char *start, char *end){
    for( ; start < end; ++start,--end){
        *start = *start ^ *end;
        *end = *start ^ *end;
        *start = *start ^ *end;
    }
}

void reverseWords(char *s){
    char *start,*end;
    start = s;
    end = s;
    while(*end != '\0')    ++end;
    reverseWord(s,end - 1);
    end = start;
    while(*end != '\0'){
        while(*end == ' ')  ++end;
        char* wordbegin = end;
        while(*end != ' ' && *end != '\0')  ++end;
        reverseWord(wordbegin,end-1);
        char* shift = end - wordbegin + start - 1;
        while(start <= shift)    *start++ = *wordbegin++;
        if(*end == '\0'){
            *start = '\0';
            break;
        }else{
            *start = ' ';
            ++start;
            ++end;
        }
    }
    if(*(start - 1) == ' ')   *(start - 1) = '\0';
}

最后一句if(*(start - 1) == ' ') *(start - 1) = '\0';感觉不优雅，加上这句是因为只要是****string按照前面的程序执行结果都会是string*

整个算法就是，先把整个字符串逆序，然后再将各单词逆序，先逆序单词再逆序整个字符串也行。