【数据结构连载一栈】【四则运算--后缀表达式】golang

package main

import (
	"fmt"
	"strconv"
	"strings"
)

type Node struct {
	data interface{}
	next *Node
}
type LinkedStack struct {
	length int
	head   *Node
}

func NewLinkedStack() LinkedStack {
	return LinkedStack{length: 0, head: nil}
}

func (s *LinkedStack) Clear() {
	s.length = 0
	s.head = nil
}

func (s *LinkedStack) Empty() bool {
	return s.head == nil
}

func (s *LinkedStack) Get() interface{} {
	if s.Empty() {
		panic("栈为空")
	}
	return s.head.data
}

func (s *LinkedStack) Push(data interface{}) {
	newNode := Node{
		data: data,
	}
	if !s.Empty() {
		newNode.next = s.head
	}
	s.head = &newNode
	s.length++
}

func (s *LinkedStack) Pop() interface{} {
	if s.Empty() {
		panic("栈为空")
	}
	data := s.head.data
	s.head = s.head.next
	s.length--
	return data
}

func (s *LinkedStack) Length() int {
	return s.length
}

// 判断元素是否存在
func elemExist(s string, l []string) bool {
	for _, v := range l {
		if v == s {
			return true
		}
	}
	return false
}

// 处理栈中的数据
func priorityExp(s string, stack *LinkedStack) (sList []string) {
	if s == ")" {
		for {
			if stack.Empty() {
				break
			}
			cur := stack.Pop()
			if cur == "(" {
				return
			}
			sList = append(sList, cur.(string))
		}
	} else if s == "+" || s == "-" {
		for {
			if stack.Empty() {
				break
			}
			if stack.Get() == "(" {
				break
			}
			sList = append(sList, stack.Pop().(string))
		}
	} else {
		for {
			if stack.Empty() {
				break
			}
			if stack.Get() != "/" || stack.Get() != "*" {
				break
			}
			sList = append(sList, stack.Pop().(string))
		}
	}
	stack.Push(s)
	return
}
func InvPolSufExp(expression string) string {
	stack := NewLinkedStack()
	strs := make([]string, 0)
	for _, v := range strings.Split(expression, " ") {
		if elemExist(v, []string{"+", "-", "*", "/", "(", ")"}) == false {
			strs = append(strs, v)
		} else {
			strs = append(strs, priorityExp(v, &stack)...)
		}
	}
	for {
		if stack.Empty() {
			break
		}
		strs = append(strs, stack.Pop().(string))
	}
	return strings.Join(strs, " ")
}

// Arithmetic 四则运算
func Arithmetic(expStr string) float64 {
	stack := NewLinkedStack()
	for _, v := range strings.Split(expStr, " ") {
		if elemExist(v, []string{"+", "-", "*", "/", "(", ")"}) == false {
			var vv interface{} = v
			stack.Push(vv)
		} else {
			num1, _ := strconv.ParseFloat(stack.Pop().(string), 64)
			num2, _ := strconv.ParseFloat(stack.Pop().(string), 64)
			var num float64
			switch v {
			case "+":
				num = num2 + num1
			case "-":
				num = num2 - num1
			case "*":
				num = num2 * num1
			case "/":
				num = num2 / num1
			}
			var numRes interface{} = fmt.Sprintf("%v", num)
			stack.Push(numRes)
		}
	}
	res, _ := strconv.ParseFloat(stack.Pop().(string), 64)
	return res
}

func main() {
	// 9 3 1 - 3 * + 10 2 / * 后缀表达式
	fmt.Println(Arithmetic(InvPolSufExp("9 + ( 3 - 1 ) * 3 + 10 / 2")))
}