LeetCode-394. Decode String

LeetCode-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; 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 won't be input like ​​3a​​​ or ​​2[4]​​.

Examples:

s = "3[a]2[bc]", return "aaabcbc".s = "3[a2[c]]", return "accaccacc".s = "2[abc]3[cd]ef", return "abcabccdcdcdef".

题解：

这题很像224和227题。

用一个栈保存前面所有字符结果和前一个数字大小。

题解：

class Solution {public: string decodeString(string s) { int n = s.length(); string res = ""; stack str; int num = 0; for (int i = 0; i < n; i++) { if (s[i] >= '0' && s[i] <= '9') { num *= 10; num += s[i] - '0'; } else if (s[i] == '[') { str.push(res); str.push(to_string(num)); num = 0; res.clear(); } else if (s[i] == ']') { int k = stoi(str.top()); str.pop(); string tmp = str.top(); str.pop(); for (int j = 0; j < k; j++) { tmp += res; } res = tmp; } else { res += s[i]; } } return res; }};

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