feat : encode-and-decode-strings

Author: ekgns33

encode-and-decode-strings/ekgns33.java

@@ -0,0 +1,36 @@
+class Solution {
+  public String encode(List<String> strs) {
+    StringBuilder res = new StringBuilder();
+    for (String s : strs) {
+      res.append(s.length()).append('|').append(s);
+    }
+    return res.toString();
+  }
+
+
+  /*
+  * number + | + string
+  * read number until |
+  * move pointer, read substring
+  *
+  * tc : O(n) when n is the length of encoded string
+  * sc : O(1)
+  * */
+  public List<String> decode(String str) {
+    List<String> res = new ArrayList<>();
+    int start = 0;
+    while (start < str.length()) {
+      int cur = start;
+      //read until |
+      while (str.charAt(cur) != '|') {
+        cur++;
+      }
+      int length = Integer.parseInt(str.substring(start, cur));
+      start = cur + 1;
+      cur = start + length;
+      res.add(str.substring(start, cur));
+      start = cur;
+    }
+    return res;
+  }
+}