[LeetCode]45. Reverse Words in a String按单词翻转字符串

class Solution {
public:
    void reverseWords(string &s) {
        int n = s.size();
        vector<char*> word;
        char* c = new char[n + 1];
        strcpy(c, s.c_str());
        c[n] = ‘\0‘;
        char* delim = " ";
        char* wordp = nullptr;
        while ((wordp = strtok(c, delim)) != nullptr)
        {
            int m = strlen(wordp);
            char* tmp = new char[m + 1];
            strcpy(tmp, wordp);
            tmp[m] = ‘\0‘;
            word.push_back(tmp);
            c = nullptr;
        }
        s.clear();
        for (int i = word.size() - 1; i >= 0; --i)
            s += string(word[i]) + ‘ ‘;
        if(s.size() > 1) //注意去掉最后多加的那个空格
            s.resize(s.size() - 1);
    }
};

class Solution {
public:
    void reverseWords(string &s) {
        int n = s.size(), k = 0;
        int left = 0, right = n - 1;
        while (left < right) //reverse the whole string
            swap(s[left++], s[right--]);
        for (int i = 0; i < n;) // reverse all words
        {
            while (i < n && s[i] == ‘ ‘) ++i;
            int j = i;
            while (i < n && s[i] != ‘ ‘) ++i;
            int k = i - 1;
            while (j < k)
                swap(s[j++], s[k--]);
        }
        for (int i = 0; i < n; ++i) //remove all spaces not necessary
        {
            bool flag = false;
            while (i < n && s[i] == ‘ ‘) ++i;
            while (i < n && s[i] != ‘ ‘)
            {
                s[k++] = s[i++];
                flag = true;
            }
            if(flag) s[k++] = ‘ ‘;
        }
        if (k > 0) s.resize(k - 1);
        if (k == 0) s.clear();
    }
};

class Solution {
public:
    void reverseWords(string &s) {
        int i = 0, j = 0, k = 0, wordCount = 0;
        while (true) {
            while (i < s.size() && s[i] == ‘ ‘) ++i;
            if (i == s.size()) break;
            if (wordCount) s[j++] = ‘ ‘;
            k = j;
            while (i < s.size() && s[i] != ‘ ‘) {
                s[j] = s[i];
                ++j; ++i;
            }
            reverseWord(s, k, j - 1);
            ++wordCount;
        }
        s.resize(j);
        reverseWord(s, 0, j - 1);
    }
    void reverseWord(string &s, int i, int j) {
        while (i < j) {
            char t = s[i];
            s[i++] = s[j];
            s[j--] = t;
        }
    }
};