문제 난이도 : Easy

문제 유형 : Data Structures - String

문제 설명 간략 :

k[encoded_string] 형태의 string이 주어지고 encoded_string을 k번 반복하여 decoded string을 반환하라.

제약사항

• 1 <= s.length <= 30
• s consists of lowercase English letters, digits, and square brackets ‘[]’.
• s is guaranteed to be a valid input.
• All the integers in s are in the range [1, 300].

자바 풀이

class Solution {
    public String decodeString(String s) {

        Stack<String> strStack = new Stack<>();
        Stack<Integer> numStack = new Stack<>();
        StringBuilder res = new StringBuilder();
        StringBuilder numSb = new StringBuilder();

        int idx = 0;
        while (idx < s.length()) {
            char curLetter = s.charAt(idx);
            if (Character.isDigit(curLetter)) {
                numSb.append(curLetter);
                idx++;
            } else if (curLetter == '[') {
                numStack.push(Integer.parseInt(numSb.toString()));
                strStack.push(res.toString());
                numSb = new StringBuilder();
                res = new StringBuilder();
                idx++;
            } else if (curLetter == ']') {
                StringBuilder temp = new StringBuilder(strStack.pop());
                int repeatTimes = numStack.pop();
                for (int i = 0; i < repeatTimes; i++) {
                    temp.append(res);
                }
                res = temp;
                idx++;
            } else {
                res.append(s.charAt(idx++));
            }
        }
        return res.toString();
    }
}

출처

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