我尝试从头开始编写此代码、编码并运行它,但它似乎不起作用。这被分配为课堂上的实验室工作。要求是: 使用堆栈和堆栈操作(用户定义)实现后缀评估。我认为我的程序的算法是正确的,但它总是给我错误的答案。这是我的代码。
public class StackApplication {
public static class Stack<T> {
private int top = 0;
private final static int stackMax=100;
// highest index of stk array
private Object[] stk = new Object[stackMax+1];
//Elements must be cast back.
public Stack() { // constructor
}
public boolean isEmpty(){
if (top==0) return true;
else return false;
}
public void push(T el) {
if(top==stackMax)
System.out.println("Stack push overflow error");
else top=top+1;
stk[top]=el;
}
public T pop(){
if(isEmpty()){
System.out.println("Stack push underflow error");
return null;
}
else top=top-1;
return(T)stk[top+1];
}
public T top(){
if(isEmpty()){
//System.out.println("Stack empty");
return null;
}
else return (T)stk[top];
}
}
public static boolean isOperator(char c){
return(c=='+' || c=='-' || c=='/' || c=='*' || c=='^');
}
public static double evaluate(double x, char o, double y) {
double result=0;
switch(o) {
case '+' : result=x+y; break;
case '-' : result=x-y; break;
case '*' : result=x*y; break;
case '/' : result=x/y; break;
case '^' : result=Math.pow(x, y); break;
default : break;
}
return result;
}
public static void main(String[] args) {
Scanner console=new Scanner(System.in);
Stack<Double> s=new Stack<Double>();
System.out.println("Input Postfix form to evaluate:");
String inp=console.nextLine();
char[] chararray=inp.toCharArray();
double b,a;
for(int i=0; i<chararray.length; i++) {
if(!isOperator(chararray[i]))
s.push((double)chararray[i]);
else {
b=s.pop();
a=s.pop();
double c=evaluate(a, chararray[i], b);
s.push(c);
}
}
System.out.println(" " +s.pop());
}
}
示例输出:输入后缀形式以评估:
23+ (Input)
101.0 (Output)
5.0 (Expected output)