牛客最近来了一个新员工Fish,每天早晨总是会拿着一本英文杂志,写些句子在本子上。同事Cat对Fish写的内容颇感兴趣,有一天他向Fish借来翻看,但却读不懂它的意思。例如,“student. a am I”。后来才意识到,这家伙原来把句子单词的顺序翻转了,正确的句子应该是“I am a student.”。Cat对一一的翻转这些单词顺序可不在行,你能帮助他么?
按照上一题的思路:
class Solution {
public:
string ReverseSentence(string str) {
if(str.size() == 0) return "";
vector<int> index;
for(int i = 0; i < str.size(); i++) {
if(str[i] == ' ') index.push_back(i);
}
if(index.empty()) return str;
reverse(str.begin(), str.begin()+index[0]);
for(int i = 1 ; i < index.size(); i++) {
reverse(str.begin()+index[i-1]+1, str.begin()+index[i]);
}
reverse(str.begin()+index[index.size()-1]+1, str.end());
reverse(str.begin(), str.end());
return str;
}
};
库函数stringstream:
class Solution {
public:
string ReverseSentence(string str) {
// 预处理
if (str.empty()) return str;
int i = 0, sz = str.size();
while(i < sz && str[i] == ' ') ++i;
if (i == sz) return str;
istringstream ss(str);
vector<string> ret;
string s;
// 拆分单词
while (ss >> s)
ret.push_back(s);
reverse(ret.begin(), ret.end());
ostringstream oss;
// 合并成字符串
for (int i=0; i<ret.size()-1; ++i)
oss << ret[i] << ' ';
oss << ret.back();
return oss.str();
}
};