Eric 的小站

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输入：s = "the sky is blue"
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输出："blue is sky the"

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输入：s = "  hello world  "
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输出："world hello"
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解释：反转后的字符串中不能存在前导空格和尾随空格。

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输入：s = "a good   example"
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输出："example good a"
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解释：如果两个单词间有多余的空格，反转后的字符串需要将单词间的空格减少到仅有一个。

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class Solution {
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public:
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    string reverseWords(string s) {
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        bool flag = false;
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        string str_ = "";
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        vector<string> result;
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        for (auto str : s) {
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            if (str != ' ') {
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                flag = true;
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                str_.push_back(str);
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            }
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            else if (str == ' ' && flag ) {
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                result.push_back(str_);
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                str_.clear();
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                flag = false;
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            }
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        }
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        if (flag && !str_.empty()) {
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            result.push_back(str_);
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        }
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        string reversed = "";
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        for (auto it = result.rbegin(); it != result.rend(); ++it) {
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            reversed += *it;
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            if (it + 1 != result.rend()) reversed += " ";
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        }
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        return reversed;
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    }
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};