·当读到数字直接送至输出队列中
·当读到运算符t时，
a. 将栈中所有优先级高于或等于t的运算符弹出，送到输出队列；
b. t进栈
·读到左括号时总是将它压入栈中
·读到右括号时，将靠近栈顶的第一个左括号上面的运算符全部依次弹出，送至输出队列后，再丢弃左括号。
运用后缀表达式进行计算的具体做法：
·建立一个栈S
·从左到右读后缀表达式，读到数字就将它转换为数值压入栈S中，读到运算符则从栈中依次弹出两个数分别到Y和X，然后以“X 运算符 Y”的形式计算机出结果，再压加栈S中
·如果后缀表达式未读完，就重复上面过程，最后输出栈顶的数值则为结束
我有个计算器程序，是先把中缀转后缀的。------------------
import java.awt.event.ActionEvent
import java.awt.event.ActionListener
import javax.swing.JButton
import javax.swing.JFrame
import javax.swing.JTextField
class Stack_Float
{
float nums[]
int top
Stack_Float()
{
nums = new float[50]
top = -1
}
boolean IsEmpty()
{
if (top == -1)
return true
else
return false
}
float Pop_Stack()
{
if (top == -1)
{
return 0
}
top--
return nums[top + 1]
}
float GetTop()
{
return nums[top]
}
void Push_Stack(float num)
{
if (top == 49)
return
top++
nums[top] = num
}
}
class Stack_Char
{
char str[]
int top
Stack_Char()
{
str = new char[50]
top = -1
}
boolean CanPush(char c)
{
int temp = top
if (c == '(')
{
while (temp != -1)
{
if (str[temp] == '(')
{
return false
}
temp--
}
}
temp = top
if (c == '[')
{
while (temp != -1)
{
if (str[temp] == '[' || str[temp] == '(')
{
return false
}
temp--
}
}
if (c == '{')
{
while (temp != -1)
{
if (str[temp] == '{' || str[temp] == '[' || str[temp] == '(')
{
return false
}
temp--
}
}
return true
}
boolean IsEmpty()
{
if (top == -1)
return true
else
return false
}
void Push_Stack(char ch)
{
if (top == 49)
return
top++
str[top] = ch
}
char Pop_Stack()
{
if (top == -1)
return '\0'
top--
return str[top + 1]
}
char GetTop()
{
if (top == -1)
{
System.out.print("error")
System.exit(0)
}
return str[top]
}
}
public class jisuanqi extends javax.swing.JFrame implements ActionListener
{
JTextField text = new JTextField()
JTextField text1 = new JTextField()
JButton jButton1 = new JButton()
JButton jButton2 = new JButton()
JButton jButton3 = new JButton()
JButton jButton4 = new JButton()
JButton jButton5 = new JButton()
JButton jButton6 = new JButton()
JButton jButton7 = new JButton()
JButton jButton8 = new JButton()
JButton jButton9 = new JButton()
JButton jButton10 = new JButton()
JButton jButton11 = new JButton()
JButton jButton12 = new JButton()
JButton jButton13 = new JButton()
JButton jButton14 = new JButton()
JButton jButton15 = new JButton()
JButton jButton16 = new JButton()
JButton jButton17 = new JButton()
JButton jButton18 = new JButton()
JButton jButton19 = new JButton()
JButton jButton20 = new JButton()
JButton jButton21 = new JButton()
JButton jButton22 = new JButton()
String show = ""
public jisuanqi()
{
initComponents()
}
char[] TranSmit(char str[])
{
char houzhui[] = new char[50]// 存放后缀表达式的字符串
int i = 0, j = 0
char c = str[i]
Stack_Char s = new Stack_Char()// 存放运算符的栈
while (c != '=') // 对算术表达式扫描未结束时
{
if (c >= '0' &&c <= '9')
{
while (c >= '0' &&c <= '9')// 数字直接入栈
{
houzhui[j] = c
j++
i++
c = str[i]
}
houzhui[j] = '#'// 用#隔开数字
j++
}
switch (c) // 扫描到运算符时
{
case '+':
case '-':
case '*':
case '/':
case '(':
case '[':
case '{':
if (s.IsEmpty() == true) // 栈空,直接入栈
{
s.Push_Stack(c)
i++
c = str[i]
break
}
if (ComPare(s.GetTop(), c) == -1) {
s.Push_Stack(c)// 入栈
i++
c = str[i]
break
}
if (ComPare(s.GetTop(), c) == 1) {
houzhui[j] = s.Pop_Stack()// 出栈元素存入后缀表达式
j++
break
}
case ')': // 扫描到 )
while (s.GetTop() != '(') // 未扫描到 ( 时,出栈
{
houzhui[j] = s.Pop_Stack()
j++
}
s.Pop_Stack()// '(' 出栈
i++
c = str[i]
break
case ']': // 扫描到 ]
while (s.GetTop() != '[') // 未扫描到 [ 时,出栈
{
houzhui[j] = s.Pop_Stack()
j++
}
s.Pop_Stack()// '[' 出栈
i++
c = str[i]
break
case '}': // 扫描到 }
while (s.GetTop() != '{') // 未扫描到 { 时,出栈
{
houzhui[j] = s.Pop_Stack()
j++
}
s.Pop_Stack()// '{' 出栈
i++
c = str[i]
break
}
}
while (s.IsEmpty() != true)// 把剩余的运算符直接出栈
{
houzhui[j] = s.Pop_Stack()
j++
}
houzhui[j] = '='// 后缀表达式后面加 =
j++
houzhui[j] = '\0'
j++
return houzhui
}
float Count(char str[])
{
Stack_Float s = new Stack_Float()// 定义存放数字的栈
char c = str[0]
int i = 0
float result = 0, temp, left, right
while (c != '=') // 未扫描到 = 时
{
if (c >= '0' &&c <= '9')// 扫描到数字
{
temp = 0
while (c != '#')// 未读到分隔符时
{
temp = temp * 10 + c - '0'
i++
c = str[i]
}
s.Push_Stack(temp)// 进栈
}
switch (c)// 扫描到运算符时
{
case '+':
{
result = s.Pop_Stack() + s.Pop_Stack()// 2个数字出栈相加
s.Push_Stack(result)// 最后得数进栈
break
}
case '-':
{
right = s.Pop_Stack()// 右操作数出栈
left = s.Pop_Stack()// 左操作数出栈
result = left - right
s.Push_Stack(result)
break
}
case '*':
{
result = s.Pop_Stack() * s.Pop_Stack()// 2个数字出栈相乘
s.Push_Stack(result)
break
}
case '/':
{
right = s.Pop_Stack()// 右操作数出栈
left = s.Pop_Stack()// 左操作数出栈
result = left / right
s.Push_Stack(result)
break
}
}
i++
c = str[i]
}
return result
}
int ComPare(char a, char b) // 判断运算符的优先级函数
{
int s[][] = {// 栈顶元素高于算术表达式中的元素时, 返回 1,否则返回 -1
{ 1, 1, -1, -1, -1, 1, -1, 1, -1, 1 },
{ 1, 1, -1, -1, -1, 1, -1, 1, -1, 1 },
{ 1, 1, 1, 1, -1, 1, -1, 1, -1, 1 },
{ 1, 1, 1, 1, -1, 1, -1, 1, -1, 1 },
{ -1, -1, -1, -1, -1, -1, -1, -1, -1, -1 },
{ 1, 1, 1, 1, -1, 1, -1, -1, -1, -1 },
{ -1, -1, -1, -1, -1, -1, -1, -1, -1, -1 },
{ 1, 1, 1, 1, -1, -1, -1, -1, -1, 1 },
{ -1, -1, -1, -1, -1, -1, -1, -1, -1, -1 },
{ 1, 1, 1, 1, -1, -1, -1, -1, -1, -1 } }
char x1[] = { '+', '-', '*', '/', '(', ')', '[', ']', '{', '}' }// 栈顶元素
char x2[] = { '+', '-', '*', '/', '(', ')', '[', ']', '{', '}' }// 算术表达式中的元素
int k = 0, m, n = 0
for (m = 0m <10m++) // 查找2个进行比较的运算符在表中的位置,并返回比较结果
{
for (n = 0n <10n++)
{
if (x1[m] == a &&x2[n] == b)
{
k = 1
break// 找到比较结果后,跳出循环
}
}
if (k == 1)
break
}
return s[m][n]// 返回比较结果
}
public void actionPerformed(ActionEvent e)
{
if (e.getSource() == jButton1)
{
show += "1"
text.setText(show)
}
if (e.getSource() == jButton2)
{
show += "2"
text.setText(show)
}
if (e.getSource() == jButton3)
{
show += "3"
text.setText(show)
}
if (e.getSource() == jButton4)
{
show += "4"
text.setText(show)
}
if (e.getSource() == jButton5)
{
show += "5"
text.setText(show)
}
if (e.getSource() == jButton6)
{
show += "6"
text.setText(show)
}
if (e.getSource() == jButton7)
{
show += "7"
text.setText(show)
}
if (e.getSource() == jButton8)
{
show += "8"
text.setText(show)
}
if (e.getSource() == jButton9)
{
show += "9"
text.setText(show)
}
if (e.getSource() == jButton10)
{
show += "0"
text.setText(show)
}
if (e.getSource() == jButton11)
{
show += "+"
text.setText(show)
}
if (e.getSource() == jButton12)
{
show += "-"
text.setText(show)
}
if (e.getSource() == jButton13)
{
show += "*"
text.setText(show)
}
if (e.getSource() == jButton14)
{
show += "/"
text.setText(show)
}
if (e.getSource() == jButton15)
{
show += "("
text.setText(show)
}
if (e.getSource() == jButton16)
{
show += ")"
text.setText(show)
}
if (e.getSource() == jButton17)
{
show += "["
text.setText(show)
}
if (e.getSource() == jButton18)
{
show += "]"
text.setText(show)
}
if (e.getSource() == jButton19)
{
show += "{"
text.setText(show)
}
if (e.getSource() == jButton20)
{
show += "}"
text.setText(show)
}
if (e.getSource() == jButton21)
{
show = ""
text.setText("")
text1.setText("")
}
if (e.getSource() == jButton22)
{
show += "="
text.setText(show)
char str1[] = new char[50]
char str2[] = new char[50]
float result = 0
str1 = show.toCharArray()
str2 = TranSmit(str1)
result = Count(str2)
text1.setText((new String(str2)).trim())
text.setText("" + result)
show = ""
}
}
private void initComponents()
{
text.setBounds(10, 10, 270, 30)
text1.setBounds(10, 50, 270, 30)
jButton1.setBounds(10, 90, 60, 25)
jButton2.setBounds(80, 90, 60, 25)
jButton3.setBounds(150, 90, 60, 25)
jButton4.setBounds(220, 90, 60, 25)
jButton5.setBounds(10, 120, 60, 25)
jButton6.setBounds(80, 120, 60, 25)
jButton7.setBounds(150, 120, 60, 25)
jButton8.setBounds(220, 120, 60, 25)
jButton9.setBounds(10, 150, 60, 25)
jButton10.setBounds(80, 150, 60, 25)
jButton11.setBounds(150, 150, 60, 25)
jButton12.setBounds(220, 150, 60, 25)
jButton13.setBounds(10, 180, 60, 25)
jButton14.setBounds(80, 180, 60, 25)
jButton15.setBounds(150, 180, 60, 25)
jButton16.setBounds(220, 180, 60, 25)
jButton17.setBounds(150, 210, 60, 25)
jButton18.setBounds(220, 210, 60, 25)
jButton19.setBounds(10, 210, 60, 25)
jButton20.setBounds(80, 210, 60, 25)
jButton21.setBounds(10, 240, 60, 25)
jButton22.setBounds(80, 240, 60, 25)
jButton1.setText("1")
jButton2.setText("2")
jButton3.setText("3")
jButton4.setText("4")
jButton5.setText("5")
jButton6.setText("6")
jButton7.setText("7")
jButton8.setText("8")
jButton9.setText("9")
jButton10.setText("0")
jButton11.setText("+")
jButton12.setText("-")
jButton13.setText("*")
jButton14.setText("/")
jButton15.setText("(")
jButton16.setText(")")
jButton17.setText("[")
jButton18.setText("]")
jButton19.setText("{")
jButton20.setText("}")
jButton21.setText("CE")
jButton22.setText("=")
jButton1.addActionListener(this)
jButton2.addActionListener(this)
jButton3.addActionListener(this)
jButton4.addActionListener(this)
jButton5.addActionListener(this)
jButton6.addActionListener(this)
jButton7.addActionListener(this)
jButton8.addActionListener(this)
jButton9.addActionListener(this)
jButton10.addActionListener(this)
jButton11.addActionListener(this)
jButton12.addActionListener(this)
jButton13.addActionListener(this)
jButton14.addActionListener(this)
jButton15.addActionListener(this)
jButton16.addActionListener(this)
jButton17.addActionListener(this)
jButton18.addActionListener(this)
jButton19.addActionListener(this)
jButton20.addActionListener(this)
jButton21.addActionListener(this)
jButton22.addActionListener(this)
add(text)
add(text1)
add(jButton1)
add(jButton2)
add(jButton3)
add(jButton4)
add(jButton5)
add(jButton6)
add(jButton7)
add(jButton8)
add(jButton9)
add(jButton10)
add(jButton11)
add(jButton12)
add(jButton13)
add(jButton14)
add(jButton15)
add(jButton16)
add(jButton17)
add(jButton18)
add(jButton19)
add(jButton20)
add(jButton21)
add(jButton22)
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE)
setLayout(null)
setBounds(300, 300, 300, 300)
setVisible(true)
}
public static void main(String args[])
{
new jisuanqi()
}
}
