package com.dbc;
import java.util.Stack;
public class DecodeString {
public String decodeString(String s) {
Stack stack = new Stack<>();
for (int i = 0; i < s.length(); i++) {
if (s.charAt(i) == ']') {
StringBuilder subStr = new StringBuilder();
while (!stack.isEmpty() && !stack.peek().equals("[")) subStr.insert(0, stack.pop());
if (!stack.isEmpty()) {
stack.pop();
StringBuilder numStr = new StringBuilder();
while (!stack.isEmpty() && stack.peek().length() == 1 && Character.isDigit(stack.peek().charAt(0))) numStr.insert(0, stack.pop());
int num = Integer.parseInt(numStr.toString());
for (int j = 0; j < num; j++) stack.add(subStr.toString());
}
} else {
stack.add(Character.toString(s.charAt(i)));
}
}
StringBuilder res = new StringBuilder();
while (!stack.isEmpty()) {
res.insert(0, stack.pop());
}
return res.toString();
}
}