package q150

import "strconv"

func evalRPN(tokens []string) int {
	stack := make([]int, 0, len(tokens)/2)
	for _, s := range tokens {
		height := len(stack)

		switch s {
		case "+":
			stack[height-2] += stack[height-1]
		case "-":
			stack[height-2] -= stack[height-1]
		case "*":
			stack[height-2] *= stack[height-1]
		case "/":
			stack[height-2] /= stack[height-1]
		default:
			num, _ := strconv.ParseInt(s, 10, strconv.IntSize)
			stack = append(stack, int(num))
			continue
		}
		stack = stack[:height-1]
	}
	return stack[0]
}

var _ = evalRPN