LeetCode Reverse Words in a String

class Solution {
public:
    void reverseWords(string &s) {
        int len = s.length();
        reverse(s.begin(), s.end());
        int wpos = 0;
        for (int p=0, q=0; p < len; p = q) {
            while ((p<len) && (s[p] == ' ')) p++;
            q = p;
            while ((q<len) && (s[q] != ' ')) q++;
            reverse(s.begin() + p, s.begin() + q);
            if (wpos != 0 && p < q) s[wpos++] = ' ';
            for (int i=p; i<q; i++) {
                s[wpos++] = s[i];
            }
        }
        if (wpos != len) s = s.substr(0, wpos);
    }
};

还要处理多余空格

第二轮：

艹怎么感觉代码写的反而多了

void reverse(char* s, int start, int end) {
    int p = start;
    int q = end-1;
    while (p < q) {
        char t = s[p];
        s[p] = s[q];
        s[q] = t;
        p++, q--;
    }
}
void reverseWords(char *s) {
    if (s == NULL) {
        return;
    }
    int wpos = 0;
    int rpos = 0;
    int inWord = 0;
    int last = 0;
    char ch = 0;
    while ((ch = s[rpos]) != '\0') {
        if (inWord) {
            if (ch == ' ') {
                // one word end, reverse it
                reverse(s, last, wpos);
                inWord = 0;
            } else {
                // word continue
                s[wpos++] = ch;
            }
        } else {
            if (ch == ' ') {
                // skip space
            } else {
                // one word begin
                inWord = 1;
                if (wpos>0) {
                    s[wpos++] = ' ';    // space between last word
                }
                last = wpos;        // mark where word begin
                s[wpos++] = s[rpos];
            }
        }
        rpos++;
    }
    s[wpos] = '\0';
    if (wpos > 0 && s[rpos-1] != ' ') {
        // reverse last word
        reverse(s, last, wpos);
    } 
    
    // reverse whole string
    reverse(s, 0, wpos);
}