Evaluate an arithmetic expression written in Reverse Polish Notation (postfix form).
Evaluate Reverse Polish Notation
You are given an arithmetic expression in Reverse Polish Notation (RPN). In this notation, every operator follows its operands.
Your task is to evaluate the expression and return the final integer result.
Supported operators:
+: addition-: subtraction*: multiplication/: integer division that truncates toward zero
Assume the input expression is valid and there is exactly one final result.
Input Format
- A list of tokens representing an RPN expression.
- Each token is either:
- an integer, or
- one of
+,-,*,/.
Output Format
Return a single integer: the value of the expression.
Constraints
- The expression is valid.
- Division truncates toward zero.
- Intermediate and final values fit in standard 32-bit signed integer range for interview purposes.
Example 1
Input
["2","1","+","3","*"]
Output
9
Explanation
First compute 2 + 1 = 3, then 3 * 3 = 9.
Example 2
Input
["4","13","5","/","+"]
Output
6
Explanation
First compute 13 / 5 = 2, then 4 + 2 = 6.
Show 1 more example
Example 3
Input
["10","6","9","3","+","-11","*","/","*","17","+","5","+"]
Output
22
Explanation
Evaluate the expression left to right using a stack of operands.
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