golang力扣leetcode 150.逆波兰表达式求值

package main
import "strconv"
func evalRPN(tokens []string) int {
  if len(tokens) == 0 {
    return 0
  }
  stack := make([]int, 0, len(tokens))
  for i := 0; i < len(tokens); i++ {
    val := tokens[i]
    switch val {
    case "+", "-", "*", "/":
      a2 := stack[len(stack)-1]
      stack = stack[:len(stack)-1]
      a1 := stack[len(stack)-1]
      stack = stack[:len(stack)-1]
      result := 0
      switch val {
      case "+":
        result = a1 + a2
      case "-":
        result = a1 - a2
      case "*":
        result = a1 * a2
      case "/":
        result = a1 / a2
      }
      stack = append(stack, result)
    default:
      v, _ := strconv.Atoi(val)
      stack = append(stack, v)
    }
  }
  return stack[0]
}
func main() {
}