本文主要是介绍LeetCode75——Day26，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！
文章目录
- 一、题目
- 二、题解
一、题目
394. Decode String
Given an encoded string, return its decoded string.
The encoding rule is: k[encoded_string], where the encoded_string inside the square brackets is being repeated exactly k times. Note that k is guaranteed to be a positive integer.
You may assume that the input string is always valid; there are no extra white spaces, square brackets are well-formed, etc. Furthermore, you may assume that the original data does not contain any digits and that digits are only for those repeat numbers, k. For example, there will not be input like 3a or 2[4].
The test cases are generated so that the length of the output will never exceed 105.
Example 1:
Input: s = “3[a]2[bc]”
Output: “aaabcbc”
Example 2:
Input: s = “3[a2[c]]”
Output: “accaccacc”
Example 3:
Input: s = “2[abc]3[cd]ef”
Output: “abcabccdcdcdef”
Constraints:
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].
二、题解
class Solution {
public:string decodeString(string s) {string ans;stack<pair<int, int>> stk;int count = 0;for (auto x : s) {if (isdigit(x)) count = 10 * count + (x - '0');else if (x == '[') {stk.push({count, ans.size()});count = 0;}else if (isalpha(x)) ans += x;else if (x == ']') {int n = stk.top().first;string str = ans.substr(stk.top().second, ans.size() - stk.top().second);for (int i = 0; i < n - 1; i++) {ans += str;}stk.pop();}}return ans;}
};
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