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leetcode557. reverse words in a string iii Two pointers stringstream 总结

admin 11月 14, 2020 0

Given a string, you need to reverse the order of characters in each word within a sentence while still preserving whitespace and initial word order.

Example 1:

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Input: "Let's take LeetCode contest"
Output: "s'teL ekat edoCteeL tsetnoc"

Note: In the string, each word is separated by single space and there will not be any extra space in the string.

my code in cpp

注意如果right到了size的时候,要直接s.begin()+right,不然最后一个字母不会翻转的!

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string (string s) { 
    int left = -1, right = 0;
    while (++left<(int)s.size())
    {
        right = left;
        
        while (right<s.size()  && s[right++] != ' ');
        //翻转单词
        if (right == s.size()) 
            reverse(s.begin() + left, s.begin() + right);
        else 
            reverse(s.begin() + left, s.begin() + right-1);
        left = right - 1;
    }
    return s;
}

Two pointers

lc in cpp

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string (string s) {
    int start = 0, end = 0, n = s.size();
    while (start < n && end < n) {
        while (end < n && s[end] != ' ') ++end;
        for (int i = start, j = end - 1; i < j; ++i, --j) {
            swap(s[i], s[j]);
        }
        start = ++end;
    }
    return s;
}

stringstream

  1. string转istringstream
  2. >> 操作符重载,一直读取到空格的字符串,作为一个string
  3. string::pop_back():从字符串移除末字符。等价于 erase(end() - 1, 1) 。若字符串为空则行为未定义。
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    string (string s) {
        string res = "", t = "";
        istringstream is(s);
        while (is >> t) {
            reverse(t.begin(), t.end());
            res += t + " ";
        }
        res.pop_back();//这里要将末尾的空格删去
        return res;
    }

总结

这题是151-Reverse-Words-in-a-String的简单版本.

  1. Reverse+STL
  2. Reverse+Two pointers
  3. stringstream
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