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Parse Lisp Expression - Practice Coding | SlaveCode

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736. Parse Lisp Expression

Hard

50 Points

Hash Table

String

Stack

Recursion

You are given a string expression representing a Lisp-like expression to return the integer value of. The syntax for these expressions is given as follows.

Examples

Example 1

Input: expression = "(let x 2 (mult x (let x 3 y 4 (add x y))))" Output: 14 Explanation: In the expression (add x y), when checking for the value of the variable x, we check from the innermost scope to the outermost in the context of the variable we are trying to evaluate. Since x = 3 is found first, the value of x is 3.

Example 2

Input: expression = "(let x 3 x 2 x)" Output: 2 Explanation: Assignment in let statements is processed sequentially.

Example 3

Input: expression = "(let x 1 y 2 x (add x y) (add x y))" Output: 5 Explanation: The first (add x y) evaluates as 3, and is assigned to x. The second (add x y) evaluates as 3+2 = 5.

Constraints

1 <= expression.length <= 2000
There are no leading or trailing spaces in expression.
All tokens are separated by a single space in expression.
The answer and all intermediate calculations of that answer are guaranteed to fit in a 32-bit integer.
The expression is guaranteed to be legal and evaluate to an integer.

736. Parse Lisp Expression

Hard

50 Points

Hash Table

String

Stack

Recursion

You are given a string expression representing a Lisp-like expression to return the integer value of. The syntax for these expressions is given as follows.

Examples

Example 1

Input: expression = "(let x 2 (mult x (let x 3 y 4 (add x y))))" Output: 14 Explanation: In the expression (add x y), when checking for the value of the variable x, we check from the innermost scope to the outermost in the context of the variable we are trying to evaluate. Since x = 3 is found first, the value of x is 3.

Example 2

Input: expression = "(let x 3 x 2 x)" Output: 2 Explanation: Assignment in let statements is processed sequentially.

Example 3

Input: expression = "(let x 1 y 2 x (add x y) (add x y))" Output: 5 Explanation: The first (add x y) evaluates as 3, and is assigned to x. The second (add x y) evaluates as 3+2 = 5.

Constraints

1 <= expression.length <= 2000
There are no leading or trailing spaces in expression.
All tokens are separated by a single space in expression.
The answer and all intermediate calculations of that answer are guaranteed to fit in a 32-bit integer.
The expression is guaranteed to be legal and evaluate to an integer.