字符串变形题解

class Transform {
public:
string trans(string s, int n) {
  // write code here
  if(n==0) return s;
  reverse(s.begin(),s.end());  //翻转整个字符串
  for (int i=0;i<n;i++){
      int j=i;
      while(j<n && s[j]!=' ') j++;
      reverse(s.begin()+i,s.begin()+j);   //翻转不是空格之外的单词
      i=j;
  }
  string res;
  for (int i=0;i<n;i++){
      if (s[i]!=' ' && s[i]<='Z' && s[i]>='A') res+=s[i]-'A'+'a';
      else if (s[i]!=' ' && s[i]>='a' && s[i]<='z') res+=s[i]-'a'+'A';
      else res+=s[i];
  }
  return res;
}
};