上代码
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package main import ( "fmt" "os" "strconv" ) type stack struct { maxCount int arr [20]interface{} top_point int //栈顶指针 } func (this *stack) push(val interface{}) { if this.maxCount-1 == this.top_point { fmt.Println("栈已经满了,无法加入") return } this.top_point++ this.arr[this.top_point] = val } func (this *stack) pop() interface{} { if this.top_point == -1 { fmt.Println("空栈,没有任何元素弹出") return nil } val := this.arr[this.top_point] this.top_point-- return val } func (this *stack) showStack() { if this.top_point == -1 { fmt.Println("栈中空无一物") return } fmt.Println("显示栈") for i := this.top_point; i >= 0; i-- { fmt.Printf("arr[%d]=%v\n", i, this.arr[i]) } } func isMark(str string) bool { if str == "+" || str == "-" || str == "/" || str == "*" { return true } return false } /** 计算函数 */ func calculate(num1, num2 interface{}, mark string) (float64) { var res, v1, v2 float64 var err1, err2 error switch num1.(type) { case string: v1, err1 = strconv.ParseFloat(num1.(string), 64) handleError(err1, "计算函数出错") case float64: v1 = num1.(float64) } switch num2.(type) { case string: v2, err2 = strconv.ParseFloat(num2.(string), 64) handleError(err2, "计算函数出错") case float64: v2 = num2.(float64) } switch mark { case "+": res = v1 + v2 case "-": res = v2 - v1 case "*": res = v1 * v2 case "/": res = v2 / v1 } return res } /** +与-优先权为0,*与/优先权为1 */ func checkPriority(mark string) int { priority := 3 //默认为3,如果为3代表用户输入错误了 switch { case mark == "+" || mark == "-": priority = 0 case mark == "*" || mark == "/": priority = 1 } return priority } func handleError(err error, why string) { if err != nil { fmt.Println(why) os.Exit(1) } } func main() { exp := "10+3/2.5+10*3-56" //四则运算表达式 //数栈 numStack := &stack{ maxCount: 20, arr: [20]interface{}{}, top_point: -1, } //符号栈 markStack := &stack{ maxCount: 20, arr: [20]interface{}{}, top_point: -1, } var num1, num2, mark interface{} //临时计算变量 var complete_str string for i := 0; i < len(exp); i++ { byte2str := string(exp[i]) is_mark := isMark(byte2str) //exp[i]必须要用string转一下,否则输出的是uint8类型的字符数字ascii码 if is_mark { if markStack.top_point == -1 { //如果是符号栈为空栈则直接入栈 markStack.push(byte2str) } else { //判断符号的优先权 cur_priority := checkPriority(byte2str) mark_stack_top := markStack.arr[markStack.top_point] if res := checkPriority(mark_stack_top.(string)); res >= cur_priority { //如果符号栈的栈顶的优先权>=当前的准备入栈的符号,我们就准备从数栈中弹出两个数 // 并且弹出符号栈的栈顶符号,进行计算,并将计算的结果压入数栈 num1 = numStack.pop() num2 = numStack.pop() mark = markStack.pop() res := calculate(num1, num2, mark.(string)) numStack.push(res) markStack.push(byte2str) } else { markStack.push(byte2str) } } } else { switch { case i == len(exp)-1: is_long_num := len(complete_str) > 0 if is_long_num { complete_str += byte2str numStack.push(complete_str) complete_str = "" } else { numStack.push(byte2str) } //numStack.push(byte2str) case i < len(exp)-1: //探测下一位是否是符号,如果是符号,那我们就正常压入数栈 next := string(exp[i+1]) is_mark := isMark(next) if !is_mark { complete_str += byte2str } else { //先判断complete_str的长度,来证明上一次的循环是否是为了一个多位数或者小数在循环 is_long_num := len(complete_str) > 0 if is_long_num { complete_str += byte2str numStack.push(complete_str) complete_str = "" } else { numStack.push(byte2str) } } } } //如果是最后一次执行 if i == len(exp)-1 { times := markStack.top_point + 1 for j := 0; j < times; j++ { num1 = numStack.pop() num2 = numStack.pop() mark = markStack.pop() res := calculate(num1, num2, mark.(string)) numStack.push(res) } } } res := numStack.pop() fmt.Printf("%s=%.2f", exp, res) //10+3/2/2.5+10*3-56=-15.400000 } |
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兰陵美酒郁金香
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