算术表达式求值

最新推荐文章于 2024-03-01 16:07:16 发布

原创最新推荐文章于 2024-03-01 16:07:16 发布 · 712 阅读

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版权声明：本文为博主原创文章，遵循 CC 4.0 BY-SA 版权协议，转载请附上原文出处链接和本声明。

文章标签：

#border #function #float #class

闲来没事的时候写了个算术表达式求值的程序，还不够完善…估计也没有时间去完善了。

用的是中缀表达式转后缀表达式，另外还有的方法是用二叉树。

Demo

/*??????????????????????????????????????????????????????????????????*/

```
#ifndef __ARITHMETIC_EXPRESSION_H
```
```
#define __ARITHMETIC_EXPRESSION_H
```
```
namespace dskit
```
```
{
```
```
    #define MAXLENEXPRESSION 100
```
```
    class ArithmeticExpression
```
```
    {
```
```
    public:
```

        ArithmeticExpression(const char* expression);

```
        int Compute();
```
```
        bool IsValidate();
```
```
    private:
```
```
        void ConvertToSuffix();
```
```
        int Priority(char a, char b);
```
```
    private:
```
```
        char m_data[MAXLENEXPRESSION];
```
```
    };
```
```
}
```
```
#endif
```

Demo

```
#include
```
```
#include
```
```
#include "arithmetic_expression.h"
```
```
#include "stack.h"
```

dskit::ArithmeticExpression::ArithmeticExpression(const char* expression)

```
{
```
```
    strcpy(m_data, expression);
```
```
}
```

int dskit::ArithmeticExpression::Compute()

```
{
```
```
    ConvertToSuffix();
```

    //Stack s = CreateStack(MAXLENEXPRESSION);

```
    
```
```
    //DisposeStack(s);
```
```
    return 0;
```
```
}
```

bool dskit::ArithmeticExpression::IsValidate()

```
{
```
```
    return false;
```
```
}
```
```
/*Is a priority b*/
```

int dskit::ArithmeticExpression::Priority(char a, char b)

```
{
```

    if( ('(' == a && ')' == b) || ('(' == b && ')' == a) )

```
        return 0;
```

    if( ('+' == a && '-' == b) || ('-' == b && '+' == a) )

```
        return 0;
```

    if( ('*' == a && '/' == b) || ('/' == b && '*' == a) )

```
        return 0;
```

    if( ('*' == a || '/' == a) && ('+' == b || '-' == b) )

```
        return 1;
```

    if( ('(' == a || ')' == a) && ('+' == b || '-' == b) )

```
        return 1;
```

    if( ('(' == a || ')' == a) && ('*' == b || '/' == b) )

```
        return 1;
```
```
    return -1;
```
```
}
```

void dskit::ArithmeticExpression::ConvertToSuffix()

```
{
```
```
    char p[MAXLENEXPRESSION];
```

    Stack s = CreateStack(MAXLENEXPRESSION);

```
    size_t index = 0;
```
```
    char* pTemp = m_data;
```
```
    for(; '/0' != *pTemp; ++pTemp)
```
```
    {    
```
```
        if(*pTemp != ' ')
```
```
        {
```

            if('(' == *pTemp || ')' == *pTemp || '+' == *pTemp || '-' == *pTemp || '*' == *pTemp || '/' == *pTemp)

```
            {
```

                if(IsEmpty(s) || '(' == *pTemp)

```
                {
```
```
                    Push(*pTemp, s);
```
```
                    continue;
```
```
                }
```
```
                if(')' == *pTemp)
```
```
                {
```

                    while(!IsEmpty(s) && Top(s) != '(')

```
                    {
```

                        p[index++] = Pop(s);

```
                    }
```

                    if(!IsEmpty(s)) Pop(s);

```
                    continue;
```
```
                } 
```
```
                
```

                int iPriority = Priority(*pTemp, Top(s));

```
                if(iPriority <= 0)
```
```
                {
```

                    p[index++] = Pop(s);

```
                    while(!IsEmpty(s))
```
```
                    {
```

                        iPriority = Priority(*pTemp, Top(s));

                        if(iPriority <= 0)

```
                        {
```

                            p[index++] = Pop(s);

```
                            
```
```
                        }
```
```
                        else
```
```
                            break;
```
```
                    }
```
```
                }
```
```
                Push(*pTemp, s);
```
```
                
```
```
            }
```
```
            else
```
```
            {
```
```
                p[index++] = *pTemp;
```
```
            }    
```
```
        }//end of if    
```
```
    }//end of for
```
```
    while(!IsEmpty(s))
```

        if(Top(s) != '(') p[index++] = Pop(s);

```
    p[index] = '/0';
```
```
    //strcpy(p, m_data);
```
```
    DisposeStack(s);
```
```
    std::cout << p << std::endl;
```
```
}
```
```
int main(int argc, char* argv[])
```
```
{
```

    dskit::ArithmeticExpression ae("1+2*3/4-8+5*7");

```
    ae.Compute();
```
```
    
```
```
    return 0;
```
```
}
```

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