Design an algorithm to encode a list of strings to a string. The encoded string is then sent over the network and is decoded back to the original list of strings.
Machine 1 (sender) has the function:
string encode(vector<string> strs) {
// ... your code
return encoded_string;
}
Machine 2 (receiver) has the function:
vector<string> decode(string s) {
//... your code
return strs;
}
So Machine 1 does:
string encoded_string = encode(strs);
and Machine 2 does:
vector<string> strs2 = decode(encoded_string);
strs2 in Machine 2 should be the same as strs in Machine 1.
Implement the encode and decode methods.
Note:
*The string may contain any possible characters out of 256 valid ascii characters. Your algorithm should be generalized enough to work on any possible characters.
*Do not use class member/global/static variables to store states. Your encode and decode algorithms should be stateless.
*Do not rely on any library method such as eval or serialize methods. You should implement your own encode/decode algorithm.
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编码:把一大堆string编成一个string
译码:把那一个string变回一大堆
对于一个string,它的长度和起始位置可以确定整个string。比如我们有: dog, cat, bird, tiger.要encode成为一个string我们可以利用特殊符号表示起始位置:3@dog3@cat4@bird5@tiger。
当然string长度可以大于9。
Decode:每次先找数字(长度)再找@,从@之后开始长度为len的substr就是一个string。
class Codec {
public:
// Encodes a list of strings to a single string.
string encode(vector<string>& strs) {
string encoded = "";
for(auto s : strs){
int len = s.size();
encoded += to_string(len) + "@" + s;
}
return encoded;
}
// Decodes a single string to a list of strings.
vector<string> decode(string s) {
vector<string> res;
int head = 0;
while(head < s.size()){
int atPos = s.find_first_of('@', head);
int len = stoi(s.substr(head, atPos - head));
res.push_back(s.substr(atPos+1, len));
head = atPos + len + 1;
}
return res;
}
};
// Your Codec object will be instantiated and called as such:
// Codec codec;
// codec.decode(codec.encode(strs));