后缀表达式求值

#include<iostream>

#include<stack>

#include<cstring>

#include<string>

using namespace std;

int judge(char popx,char x);

int func(string String,int *i);

int calculate(int x,int y,char str);

int main()

{

int n,i;

char a[6000];

stack<char>str;

str.push('#');

cin>>n;

while(n--)

{

cin>>a;

string substr="";

int j;

for(i=0;i<strlen(a);)

{

if(a[i]-'0'>=0&&a[i]-'0'<=9)

{

for(j=i;a[j]-'0'>=0&&a[j]-'0'<=9;j++)

substr+=a[j];

substr+=' ';

i=j;

}

else

{

if(judge(str.top(),a[i])==1)

{

substr+=str.top();

str.pop();

}

else

if(judge(str.top(),a[i])==2)

{

str.push(a[i]);

i++;

}

else

if(judge(str.top(),a[i])==3)

{

str.pop();

i++;

}

}

}

while(str.top()!='#')

{

substr+=str.top();

str.pop();

}

stack<int>stack1;

cout<<substr<<endl;

for(i=0;i<substr.length();i++)

{

int num=0;

if(substr[i]-'0'>=0&&substr[i]-'0'<=9)

stack1.push(func(substr,&i));

else

{

int num1=stack1.top();

stack1.pop();

int num2=stack1.top();

stack1.pop();

stack1.push(calculate(num2,num1,substr[i]));

}

}

cout<<stack1.top()<<endl;

stack1.pop();

}

}

int judge(char popx,char x)

{

if(popx=='*'||popx=='/')

{

if(x=='*'||x=='/'||x=='+'||x=='-'||x==')') //输出

return 1;

else

if(x=='(') //入栈

return 2;

}

else

if(popx=='+'||popx=='-')

{

if(x=='*'||x=='/'||x=='(')

return 2;

else

if(x=='+'||x=='-'||x==')')

return 1;

}

else

if(popx=='('&&x!=')')

return 2;

else

if(popx=='('&&x==')')

return 3; //出栈后移

else

if(popx=='#')

return 2;

}

int calculate(int x,int y,char str)

{

if(str=='+')

return x+y;

else

if(str=='-')

return x-y;

else

if(str=='*')

return x*y;

else

if(str=='/')

return x/y;

}

int func(string String,int *i)

{

int j,num=0;

for(j=*i;String[j]-'0'>=0&&String[j]-'0'<=9&&String[j]!=' ';j++)

{

num=num*10+(String[j]-'0');

}

*i=j;

return num;

}