【LeetCode】344. 反转字符串 -- 541. 反转字符串 II -- 151. 反转字符串中的单词

344. 反转字符串

class Solution {
public:
    void reverseString(vector<char>& s) {
        int n = s.size();
        
        for (int i = 0; i < n/2; i++){
            char tmp = s[i];
            s[i] = s[n-1-i];
            s[n-1-i] = tmp;
        }
    }
};

541. 反转字符串 II

class Solution {
public:
    string reverseStr(string s, int k) {
        for(int i = 0; i < s.size(); i += (2*k))
        {
            int be = i, ed = 0;
            if( (i + k - 1) < s.size()) ed = i + k - 1;
            else ed = s.size() - 1;
            while( be < ed)
            {
                int tmp  = s[be];
                s[be] = s[ed];
                s[ed] = tmp;
                be++;
                ed--;
            }

        }   
        return s;     
    }
};

151. 反转字符串中的单词

class Solution {
public:
    string reverseWords(string s) {
        vector<string> ss;
        string out_s;
        int i = 0, j = 0;
        while(i < s.size())
        {
            out_s = "";
            while(i < s.size() && s[i] == ' ') i++;
            while(i < s.size() && s[i] != ' ')
            {
                out_s = out_s + s[i];
                i++;
            }
            if(out_s != "")
            {
                ss.push_back(out_s);  
                j++;
            }          
        }
        out_s = ""; 
        out_s = ss[j-1];
        for(int k = j - 2; k >= 0; k-- )
        {
            out_s = out_s + ' ' + ss[k];
        }
        return out_s;
    }
};