[LeetCode Hot 100] LeetCode394. 字符串解码

题目描述

思路

思路：

• 碰到数字：压入数字栈，注意多位数的情况
• 碰到字母：直接拼接到res
• 遇到[：将num和res分别压入栈
• 遇到]：开始处理栈顶元素

方法一：

class Solution {
    public String decodeString(String s) {
        int num = 0;
        StringBuilder res = new StringBuilder();
        Deque<String> DigStack = new ArrayDeque<>();
        Deque<Integer> NumStack = new ArrayDeque<>();

        for (char c : s.toCharArray()) {
            if (c >= '0' && c <= '9') {
                num = num * 10 + (c - '0');
            } else if (c == '[') {
                NumStack.push(num);
                DigStack.push(res.toString());
                res.delete(0, res.length());
                num = 0;
            } else if (c == ']') {
                String item = res.toString();
                int times = NumStack.pop();
                for (int i = 0; i < times - 1; i ++) {
                    res.append(item);
                }
                res.insert(0, DigStack.pop());
            } else{
                res.append(c);
            }
        }
        return res.toString();
    }
}