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187 lines
4.3 KiB
187 lines
4.3 KiB
2 weeks ago
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package utils
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import (
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"fmt"
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"math"
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"strconv"
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"strings"
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"unicode"
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)
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func CalculateFormula(formulaExpression string) float64 {
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formulaExpression = strings.Replace(formulaExpression, " ", "", -1)
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return calculatePostfix(infix2ToPostfix(formulaExpression))
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}
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// (12.3+0.1)*2.0+2
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// 12.30.1+2.0*2+
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// 后缀式计算
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func calculatePostfix(postfix []string) float64 {
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stack := Stack{}
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fixLen := len(postfix)
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for i := 0; i < fixLen; i++ {
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nextChar := postfix[i]
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// 数字:直接压栈
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if _, err := strconv.ParseFloat(nextChar, 64); err == nil {
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stack.Push(nextChar)
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} else {
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switch nextChar {
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case "√":
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// 操作符:取出数字计算值,再将结果压栈
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num1, _ := strconv.ParseFloat(stack.Pop(), 64)
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stack.Push(fmt.Sprintf("%v", math.Sqrt(num1)))
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case "²":
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// 操作符:取出数字计算值,再将结果压栈
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num1, _ := strconv.ParseFloat(stack.Pop(), 64)
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stack.Push(fmt.Sprintf("%v", math.Pow(num1, 2)))
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case "+":
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// 操作符:取出两个数字计算值,再将结果压栈
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num1, _ := strconv.ParseFloat(stack.Pop(), 64)
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num2, _ := strconv.ParseFloat(stack.Pop(), 64)
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stack.Push(fmt.Sprintf("%v", num2+num1))
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case "-":
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// 操作符:取出两个数字计算值,再将结果压栈
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num1, _ := strconv.ParseFloat(stack.Pop(), 64)
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num2, _ := strconv.ParseFloat(stack.Pop(), 64)
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stack.Push(fmt.Sprintf("%v", num2-num1))
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case "*":
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// 操作符:取出两个数字计算值,再将结果压栈
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num1, _ := strconv.ParseFloat(stack.Pop(), 64)
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num2, _ := strconv.ParseFloat(stack.Pop(), 64)
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stack.Push(fmt.Sprintf("%v", num2*num1))
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case "/":
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// 操作符:取出两个数字计算值,再将结果压栈
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num1, _ := strconv.ParseFloat(stack.Pop(), 64)
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num2, _ := strconv.ParseFloat(stack.Pop(), 64)
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stack.Push(fmt.Sprintf("%v", num2/num1))
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}
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}
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}
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result, _ := strconv.ParseFloat(stack.Top(), 64)
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return result
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}
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// 中缀表达式转后缀表达式
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func infix2ToPostfix(expStr string) []string {
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stack := Stack{}
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postfix := make([]string, 0)
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exp := []rune(expStr)
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expLen := len(exp)
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// 遍历整个表达式
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for i := 0; i < expLen; i++ {
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char := string(exp[i])
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switch char {
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case " ":
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continue
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case "(":
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// 左括号直接入栈
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stack.Push("(")
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case ")":
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// 右括号则弹出元素直到遇到左括号
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for !stack.IsEmpty() {
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preChar := stack.Top()
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if preChar == "(" {
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stack.Pop() // 弹出 "("
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break
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}
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postfix = append(postfix, preChar)
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stack.Pop()
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}
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// 数字则直接输出
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case "0", "1", "2", "3", "4", "5", "6", "7", "8", "9", ".":
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j := i
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digit := ""
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for ; j < expLen && (unicode.IsDigit(rune(exp[j])) || "." == string(exp[j])); j++ {
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digit += string(exp[j])
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}
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postfix = append(postfix, digit)
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i = j - 1 // i 向前跨越一个整数,由于执行了一步多余的 j++,需要减 1
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default:
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// 操作符:遇到高优先级的运算符,不断弹出,直到遇见更低优先级运算符
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for !stack.IsEmpty() {
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top := stack.Top()
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if top == "(" || isLower(top, char) {
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break
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}
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postfix = append(postfix, top)
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stack.Pop()
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}
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// 低优先级的运算符入栈
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stack.Push(char)
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}
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}
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// 栈不空则全部输出
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for !stack.IsEmpty() {
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postfix = append(postfix, stack.Pop())
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}
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return postfix
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}
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// 比较运算符栈栈顶 top 和新运算符 newTop 的优先级高低
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func isLower(top string, newTop string) bool {
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// 注意 a + b + c 的后缀表达式是 ab + c +,不是 abc + +
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//优先级定义
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operatorPriority := map[string]uint16{
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"+": 0,
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"-": 0,
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"*": 1,
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"/": 1,
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"√": 3,
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"²": 3,
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"(": 5,
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}
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Priority := operatorPriority[newTop] > operatorPriority[top]
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return Priority
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//switch top {
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//case "+", "-":
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// if newTop == "*" || newTop == "/" {
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// return true
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// }
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//case "(":
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// return true
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//}
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//return false
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}
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type Stack struct {
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data [1024]string
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top int
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}
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func (s *Stack) Push(d string) {
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s.data[s.top] = d
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s.top++
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}
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func (s *Stack) Pop() (d string) {
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if s.top == 0 {
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//err = fmt.Errorf("stack is empty")
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}
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s.top--
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d = s.data[s.top]
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return
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}
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func (s *Stack) Top() (d string) {
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if s.top == 0 {
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//err = fmt.Errorf("stack is empty")
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}
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d = s.data[s.top-1]
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return
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}
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func (s *Stack) IsEmpty() bool {
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return s.top == 0
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}
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