Create 0394-decode-string.java

java/0394-decode-string.java

@@ -0,0 +1,33 @@
+class Solution {
+
+ int index = 0; 
+
+ public String decodeString(String s) {
+
+ StringBuilder decoded = new StringBuilder();
+ while (index < s.length() && s.charAt(index) != ']') {
+
+ // character is a letter of encoded
+ if (!Character.isDigit(s.charAt(index))) decoded.append(s.charAt(index++));
+
+ // character is number or [ ]
+ else {
+ int k = 0;
+
+ // case: number
+ while (index < s.length() && Character.isDigit(s.charAt(index))) k = k * 10 + s.charAt(index++) - '0';
+
+ // case: [
+ index++;
+ String answer = decodeString(s);
+
+ // case: ]
+ index++;
+
+ // add k*encoded to decoded
+ while (k-- > 0) decoded.append(answer);
+ }
+ }
+ return new String(decoded);
+ }
+}