题解 | #字符串变形#使用find_last_of和常用ASCII

class Solution {
public:
    string change(string s) {
        int len2 = s.size();
        string ret;
        for (int i = 0; i < len2; i++) {
                if (s[i] >= 'a' && s[i] <= 'z') {
                    ret += (s[i] - 32);
                } else {
                    ret += (s[i] + 32);
                }
            }
        return ret;
    }
    
    string trans(string s, int n) {
        int len = s.size();
        if (len == 0) {
            return "";
        }
        string ret = "";
        
        while(s.find_last_of(' ') != -1) {
            int pos = s.find_last_of(' ');
            string tempStr = s.substr(pos + 1);
            int lenTempStr = tempStr.size();
            ret += change(tempStr);
            ret += " ";
            s = s.substr(0, pos);
        }
        
        ret += change(s);
        return ret;
    }
};