package com.hongjindong.Stack;
public class calculate {
private int MaxSize = 20;
int[] AStack = new int[MaxSize];
int top = -1;
public void push(int Value) {//入棧
if (top >= MaxSize) {
System.out.println("The stack is full! ");
} else {
top++;
AStack[top] = Value;
}
}
public int pop() {//出棧
int temp;
if (top < 0) {
System.out.println("The stack is empty!");
return -1;
}
temp = AStack[top];
top--;
return temp;
}
public boolean IsOperator(int operator) {//判斷是否是運算符
if (operator == 43 || operator == 45 || operator == 42
|| operator == 47)
return true;
else
return false;
}
public int Priority(int operator) {//判斷優先級
if (operator == 43 || operator == 45)
return 1;
else if (operator == 42 || operator == 47)
return 2;
else
return 0;
}
public int TwoResult(int operator, int operand1, int operand2) {//兩個數的運算
switch (operator) {
case 43:
return (operand2 + operand1);
case 45:
return (operand2 - operand1);
case 42:
return (operand2 * operand1);
case 47:
return (operand2 / operand1);//注意這裏寫表達式的順序
}
return 0;
}
public static void main(String[] args) {
calculate Operator = new calculate();
calculate Operand = new calculate();
String Expression = "8*9-2*4";
int Position = 0;
int Operator1;
int Operand1 = 0;
int Operand2 = 0;
int Result = 0;
while (true) {
if (Operator.IsOperator((int) Expression.charAt(Position))) {//判斷讀入的是否是運算符
if (Operator.top != -1) {//如果運算符棧還有符號，判斷兩者的優先級
if (Operator.Priority((int) Expression.charAt(Position)) <= Operator
.Priority(Operator.AStack[Operator.top])) {//棧類的運算符優先級大，先計算
Operand1 = Operand.pop();
Operand2 = Operand.pop();
Operator1 = Operator.pop();
Operand.push(Operand.TwoResult(Operator1, Operand1,
Operand2));
}
}
Operator.push((int) Expression.charAt(Position));//運算符進棧
}
else {
Operand.push((int) Expression.charAt(Position) - 48);//整數進棧
}
Position++;
if (Position >= Expression.length())
break;
}
while (Operator.top != -1) {//出棧
Operand1 = Operand.pop();
Operand2 = Operand.pop();
Operator1 = Operator.pop();
Operand.push(Operand.TwoResult(Operator1, Operand1, Operand2));
}
Result = Operand.pop();
System.out.println("The expression result is :" + Result);
}
}
