3612. Process String with Special Operations I

Description

You are given a string s consisting of lowercase English letters and the special characters: *, #, and %.

Build a new string result by processing s according to the following rules from left to right:

• If the letter is a lowercase English letter append it to result.
• A '*' removes the last character from result, if it exists.
• A '#' duplicates the current result and appends it to itself.
• A '%' reverses the current result.

Return the final string result after processing all characters in s.

 

Example 1:

Input: s = "a#b%*"

Output: "ba"

Explanation:

i	s[i]	Operation	Current result
0	'a'	Append 'a'	"a"
1	'#'	Duplicate result	"aa"
2	'b'	Append 'b'	"aab"
3	'%'	Reverse result	"baa"
4	'*'	Remove the last character	"ba"

Thus, the final result is "ba".

Example 2:

Input: s = "z*#"

Output: ""

Explanation:

i	s[i]	Operation	Current result
0	'z'	Append 'z'	"z"
1	'*'	Remove the last character	""
2	'#'	Duplicate the string	""

Thus, the final result is "".

 

Constraints:

• 1 <= s.length <= 20
• s consists of only lowercase English letters and special characters *, #, and %.

 

Solutions

Solution: Simulation

• Time complexity: O(n)
• Space complexity: O(n)

 

JavaScript

/**
 * @param {string} s
 * @return {string}
 */
const processStr = function (s) {
  const REMOVE = '*';
  const DUPLICATE = '#';
  const REVERSE = '%';
  const operationMap = {
    [REMOVE]: arr => {
      arr.pop();

      return arr;
    },
    [DUPLICATE]: arr => {
      arr.push(...arr);

      return arr;
    },
    [REVERSE]: arr => arr.toReversed(),
    default: (arr, char) => {
      arr.push(char);

      return arr;
    },
  };
  let current = [];

  for (const char of s) {
    const operation = operationMap[char] ?? operationMap.default;

    current = operation(current, char);
  }

  return current.join('');
};