decodestring

class Solution {
    public String decodeString(String s) {
        Stack<Integer> numStack = new Stack<>();
        Stack<String> stringStack = new Stack<>();
        int k = 0;

        for (char c : s.toCharArray()) {

        if (Character.isDigit(c)) {
            k = (k * 10) + (c - '0');
            continue;
        }

        if (c == '[') {
            numStack.push(k);
            k = 0;
            stringStack.push(String.valueOf(c));
            continue;
        }

        if (c != ']') {
            stringStack.push(String.valueOf(c));
            continue;
        }

        StringBuilder temp = new StringBuilder();
        while (!stringStack.peek().equals("["))
            temp.insert(0, stringStack.pop());

        // remove the "["
        stringStack.pop();

        // Get the new string
        StringBuilder replacement = new StringBuilder();
        int count = numStack.pop();
        for (int i = 0; i < count; i++)
            replacement.append(temp);

        // Add it to the stack
        stringStack.push(replacement.toString());
        }

        StringBuilder result = new StringBuilder();
        while (!stringStack.empty()) {
        result.insert(0, stringStack.pop());
        }
        return result.toString();
    }

    }