LeetCode 271. Encode and Decode Strings(字串編解碼)
阿新 • • 發佈:2019-02-02
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
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
思路:把字串陣列按照長度+內容的格式進行編解碼。
public class Codec {
// Encodes a list of strings to a single string.
public String encode(List<String> strs) {
char[] lenstr = new char[4];
StringBuilder sb = new StringBuilder();
for(String str: strs) {
int len = str.length();
for(int j=3; j>=0; j--) {
lenstr[j] = (char)(len & 0b11111111);
len >>= 8;
}
sb.append(new String(lenstr));
sb.append(str);
}
return sb.toString();
}
// Decodes a single string to a list of strings.
public List<String> decode(String s) {
List<String> decoded = new ArrayList<>();
int pos = 0;
while (pos < s.length()) {
int len = 0;
for(int i=0; i<4; i++) len = (len<<8) + s.charAt(pos++);
decoded.add(s.substring(pos, pos+len));
pos += len;
}
return decoded;
}
}
// Your Codec object will be instantiated and called as such:
// Codec codec = new Codec();
// codec.decode(codec.encode(strs));