逆波兰计算器

来源：互联网发布：优化语文教学五环节编辑：程序博客网时间：2024/06/09 23:47
#include<iostream>#include<algorithm>#include<stack> #include<string>using namespace std;int level(char ch);int main(){    stack <char> s1, s2, s3, s4; //    char str[10];    int p1, p2;    cin>>str;    char ch;    for(int i = 0;str[i]!='\0';i++)    {         if(str[i] >='0' && str[i]<='9')         {            s1.push(str[i]);         }        if(str[i] == '(')        {            s2.push(str[i]);//左括号放入运算符堆栈        }        else if(str[i]== ')')        {            while(s2.top() != '(')            {                ch = s2.top();                s2.pop();                s1.push(ch);            }            s2.pop();        }        else if(str[i] == '+' || str[i] == '-' || str[i] == '*' || str[i] == '/')        {             if(s2.empty())            {                s2.push(str[i]);            }            else if(!s2.empty() && s2.top() == '(' || s2.top() == ')')            {                s2.push(str[i]);            }            else if(!s2.empty() && level(str[i]) > level(s2.top()))            {                s2.push(str[i]);            }            else if(!s2.empty() && level(str[i]) <= level(s2.top()))            {                ch = s2.top();                s2.pop();                s1.push(ch);                s2.push(str[i]);            }           }    }    while(!s2.empty())    {        ch = s2.top();        s2.pop();        s1.push(ch);    }//s1 从左到又数逆波兰    cout<<endl;    cout<<"逆波兰从右往左看"<<endl;    while(!s1.empty())    {        ch = s1.top();        cout<<ch<<' ';        s3.push(ch);        s1.pop();    }    cout<<endl;    /*while(!s3.empty())    {        cout<<s3.top()<<' ';        s3.pop();    }*/    while(!s3.empty())    {        if(s3.top() >= '0' && s3.top() <= '9')        {            s4.push(s3.top());            s3.pop();        }        else if(s3.top() == '+' || s3.top() == '-' || s3.top() == '*' || s3.top() == '/')        {            if(s3.top() == '+')            {s3.pop();                p1 = s4.top() - '0';                s4.pop();                p2 = s4.top() - '0';                s4.pop();                if(s3.empty())                {                    cout<<p1+p2<<endl;                }                else                {                    s4.push(char(p1+p2+48));                }            }            else if(s3.top() == '-')            {s3.pop();                p1 = s4.top() - '0';                s4.pop();                p2 = s4.top() - '0';                s4.pop();                if(s3.empty())                {                    cout<<p2-p1<<endl;                }                else                {                    s4.push(char(p2-p1+48));                }            }            else if(s3.top() == '*')            {s3.pop();                p1 = s4.top() - '0';                s4.pop();                p2 = s4.top() - '0';                s4.pop();                if(s3.empty())                {                    cout<<p1*p2<<endl;                }                else                {                    s4.push(char(p1*p2+48));                }            }            else if(s3.top() == '/')            {                s3.pop();                p1 = s4.top() - '0';                s4.pop();                p2 = s4.top() - '0';                s4.pop();                if(s3.empty())                {                    cout<<p2/p1<<endl;                }                else                {                    s4.push(char(p2/p1+48));                }            }        }    }    return 0;} int level(char ch)     //优先级判断  {         if(ch=='(')         return   0;         if(ch=='+'||ch=='-')       return   1;         if (ch=='*'||ch=='/')        return   2;    }
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