Validate abbreviations and brackets

The coding round included two short implementation problems:

1. Abbreviation validation Given a lowercase word word and a string abbr, determine whether abbr is a valid abbreviation of word.

• Letters in abbr must match the corresponding letters in word.
• A positive integer in abbr means skipping that many characters in word.
• Numbers cannot have leading zeros.
• The abbreviation is valid only if it consumes the entire word exactly.

Example:

• word = "internationalization", abbr = "i12iz4n" -> true
• word = "apple", abbr = "a2e" -> false

2. Balanced bracket validation Given a string s containing only the characters (, ), [, ], {, and }, return whether the brackets are balanced.

• Every opening bracket must be closed by the same type of bracket.
• Brackets must be closed in the correct order.
• An empty string is considered valid.

Example:

• s = "()[]{}" -> true
• s = "([)]" -> false

Part 1: Abbreviation Validation

Given a lowercase word word and a string abbr, determine whether abbr is a valid abbreviation of word.

Rules:

• Letters in abbr must match the corresponding letters in word.
• A positive integer in abbr means skipping that many characters in word.
• Numbers cannot have leading zeros.
• The abbreviation is valid only if it consumes the entire word exactly.

Constraints

• 0 <= len(word) <= 100000
• 0 <= len(abbr) <= 100000
• word contains only lowercase English letters
• abbr contains only lowercase English letters and digits
• Any numeric part of abbr must represent a positive integer with no leading zeros to be valid

Examples

Example 1

Input: ("internationalization", "i12iz4n")
Output: True

Explanation: i matches, 12 skips 12 letters, i and z match, 4 skips 4 letters, and n matches the final character.

Example 2

Input: ("apple", "a2e")
Output: False

Explanation: After matching a and skipping 2 characters, the next character in word is l, not e.

Hints

1. Use two pointers: one for word and one for abbr.
2. When you see a digit, parse the full number first, then advance the word pointer by that amount.

Part 2: Balanced Bracket Validation

Given a string s containing only the characters (, ), [, ], {, and }, return whether the brackets are balanced.

A string is balanced if:

• Every opening bracket is closed by the same type of bracket.
• Brackets are closed in the correct order.
• An empty string is considered valid.

Constraints

• 0 <= len(s) <= 100000
• s contains only the characters (, ), [, ], {, and }

Examples

Example 1

Input: "()[]{}"
Output: True

Explanation: Each bracket is correctly opened and closed.

Example 2

Input: "([)]"
Output: False

Explanation: The order is wrong: ( opens first, but ] tries to close [ before ) closes (.

Hints

1. Use a stack to keep track of the opening brackets you have not matched yet.
2. When you see a closing bracket, it must match the most recent unmatched opening bracket.