Leetcode: Ternary Expression Parser

Ternary Expression Parser



Similar Problems:


Given a string representing arbitrarily nested ternary expressions, calculate the result of the expression. You can always assume that the given expression is valid and only consists of digits 0-9, ?, :, T and F (T and F represent True and False respectively).

Note:

  1. The length of the given string is <= 10000.
  2. Each number will contain only one digit.
  3. The conditional expressions group right-to-left (as usual in most languages).
  4. The condition will always be either T or F. That is, the condition will never be a digit.
  5. The result of the expression will always evaluate to either a digit 0-9, T or F.

Example 1:

Input: "T?2:3"

Output: "2"

Explanation: If true, then result is 2; otherwise result is 3.

Example 2:

Input: "F?1:T?4:5"

Output: "4"

Explanation: The conditional expressions group right-to-left. Using parenthesis, it is read/evaluated as:

    "(F ? 1 : (T ? 4 : 5))"          "(F ? 1 : (T ? 4 : 5))"
 -> "(F ? 1 : 4)"            or   -> "(T ? 4 : 5)"
 -> "4"                           -> "4"

Example 3:

Input: "T?T?F:5:3"

Output: "F"

Explanation: The conditional expressions group right-to-left. Using parenthesis, it is read/evaluated as:

    "(T ? (T ? F : 5) : 3)"        "(T ? (T ? F : 5) : 3)"
 -> "(T ? F : 3)"           or  -> "(T ? F : 5)"
 -> "F"                         -> "F"

Github: code.dennyzhang.com

Credits To: leetcode.com

Leave me comments, if you have better ways to solve.


// Blog link: https://code.dennyzhang.com/ternary-expression-parser

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