Today I have done leetcode's December LeetCoding Challenge with cpp.

December LeetCoding Challenge 19

Description

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].

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"

Example 4:

Input: s = "abc3[cd]xyz"
Output: "abccdcdcdxyz"

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].

Solution

class Solution {
  int len;
  string decode(string &s, int &pos) {
    string result;
    while(pos < len) {
      if(islower(s[pos])) {
        result.push_back(s[pos]);
      } else if(isdigit(s[pos])) {
        int repeat = 0;
        while(isdigit(s[pos])) {
          repeat *= 10;
          repeat += s[pos] - '0';
          pos += 1;
        }
        pos += 1;
        string repeatS = decode(s, pos);
        while(repeat--) {
          result += repeatS;
        }
      } else if(s[pos] == ']') {
        return result;
      }
      pos += 1;
    }
    return result;
  }
public:
  string decodeString(string s) {
    len = s.length();
    int pos = 0;
    return decode(s, pos);
  }
};

// Accepted
// 34/34 cases passed (0 ms)
// Your runtime beats 100 % of cpp submissions
// Your memory usage beats 90.28 % of cpp submissions (6.4 MB)

2021-12-19 Daily-Challenge

December LeetCoding Challenge 19

Description

Solution