1006. Evaluate a Postfix (RPN) Expression

Medium · Stack

Evaluate a postfix expression with integer operands and the four basic operators (+, -, *, /). Use a stack.

Tokens are space-separated. For division, use truncated integer division (Python //), and assume no division by zero in test cases.

Input (stdin, JSON): { "expr": "3 4 + 5 *" }

Output (stdout): the evaluated integer result.

Example: "3 4 +" → 7; "3 4 + 5 *" → 35; "1 2 3 * +" → 7.

Examples

Example 1
Input: {"expr":"3 4 +"}
Output: 7

Example 2
Input: {"expr":"3 4 + 5 *"}
Output: 35

Constraints

• Tokens space-separated; valid RPN.
• Operands fit in 64-bit signed int.