Inverse Polish expression

A simple arithmetic suffix, and an evaluation of the suffix. has been tested

infix turn suffix:

#include <queue>
#include <iostream>
#include <stdlib.h>
#include <string>
#include <string.h>
#include <sstream>
#include <stack>

Static stack<string> ss_out;   the element used to hold the suffix expression when the//suffix is evaluated  static stack<string> ss_optr;  //infix suffix is used to store operators  static queue<string> qs;       //The element used to store suffix expression when infix suffix  string:: Const_iterator IT;

BOOLIsnum (it it) {if(*it-'0'>=0&& *it-'9'<=0)        return true; Else        return false;}//The operator between the Operation Ching () is ejected and pressed into the output queue;voidGetparenth (void){         for(; Ss_optr.top ()! ="("; Qs.push (Ss_optr.top ()), Ss_optr.pop ()) {}    if(Ss_optr.top () = ="(") Ss_optr.pop ();}voidPush_qs (void) {Qs.push (Ss_optr.top ()); Ss_optr.pop ();}voidPush_optr_top (it&bit)    {Ostringstream oss; OSS<< *it; stringtmp=Oss.str (); Ss_optr.push (TMP);}//Priority Processing: +-*/simple arithmetic, directly listed, you can also refer to the encyclopedia of the two-dimensional array to prioritize the methodvoidPush_optr (it&it) {    if(*it = ='(') Push_optr_top (IT); if(*it = ='/'){         while(!ss_optr.empty () && ss_optr.top () = ="/") Push_qs ();    Push_optr_top (IT); }    if(*it = ='*'){         while(!ss_optr.empty () && (ss_optr.top () = ="/"|| Ss_optr.top () = ="*") ) Push_qs ();    Push_optr_top (IT); }    if(*it = ='-'){         while(!ss_optr.empty () && (ss_optr.top () = ="/"|| Ss_optr.top () = ="*"|| Ss_optr.top () = ="-") ) Push_qs ();    Push_optr_top (IT); }    if(*it = ='+'){         while(!ss_optr.empty () && ss_optr.top ()! ="(") Push_qs ();    Push_optr_top (IT); }}//infix suffixvoidIntopost (string Const&str_in) {     for(IT it_in = Str_in.begin (); It_in!=str_in.end (); + +it_in)        {Ostringstream oss;  while(Isnum (it_in)) {OSS << *it_in; if(! Isnum (it_in+1) || it_in+1==Str_in.end ()) {                stringTMP =Oss.str ();                               Qs.push (TMP); //encountering symbols converts the output stream into a string into the output queue;                 Break; }            ++it_in; }        if(!Isnum (it_in)) {             if(*it_in==')') Getparenth (); //The operator between the Operation Ching () is ejected and pressed into the output queue;            Else{push_optr (it_in); }        }    }     while(!Ss_optr.empty ())        {Qs.push (Ss_optr.top ());    Ss_optr.pop (); }}

Suffix evaluation, only write support int type, did not write the template, will read:

voidclear_s (stack<string>&SS) {     while(!Ss.empty ())    {Ss.pop (); }}//Stack top 2 element operation, and the result into the stackvoidCalculate (it& it,stack<string>&ss_out) {    stringStr_tmp =Ss_out.top (); intresult = Atoi (Str_tmp.c_str ());//The top element of the stack is converted to int;Ss_out.pop (); Str_tmp=Ss_out.top ();    Ss_out.pop (); Switch(*it) {         Case '+': result = Atoi (Str_tmp.c_str ()) + result; Break;  Case '-': result = Atoi (Str_tmp.c_str ())-result; Break;  Case '*': result = Atoi (STR_TMP.C_STR ()) * result; Break;  Case '/': result = Atoi (Str_tmp.c_str ())/result; Break;    } ostringstream oss; OSS<<result; Str_tmp= Oss.str ();//The result of the calculation is converted to stringSs_out.push (str_tmp);}//Suffix expression evaluationvoidPost_val (string Const&str_post)    {clear_s (ss_out);  for(IT it_out = Str_post.begin (); It_out!=str_post.end (); + +it_out)        {Ostringstream oss;  while(Isnum (It_out)) {OSS << *it_out; if(! Isnum (it_out+1)){                stringTMP =Oss.str ();                                 Ss_out.push (TMP); //encountering symbols converts the numbers in the output stream into strings into stacks;            }            ++it_out; }        if(!Isnum (it_out)) {            if(*it_out = =',')                Continue; ElseCalculate (it_out,ss_out); }    }}

Test:

voidShow_post () { while(!Qs.empty ()) {cout<< Qs.front () <<" "<<Flush;    Qs.pop (); } cout<<Endl;}voidTest () {stringStr_post; stringstr_in; cout<<"Input infix expression:"<<Endl; CIN>>str_in;    Intopost (str_in);    Show_post (); cout<<"Input postfix expression:"<<Endl; CIN>>Str_post;    Post_val (Str_post); cout<< ss_out.top () <<Endl;}intMainvoid) {test (); return 0;}

For example, input 13+ (30-((600/2/15-2-3*4)/2) *10-50) output is 13 30 600 2/15 2-3 4 *-2/10 *-50-+

Input: 2/15 2-3 4 *-2/10 *--+ output:-37

Improved:

1. Operator precedence processing can be more general and optimized

2. Check the legality of user input

3. Evaluation can be written in the form of a template to more general

Write a lot of C, C + +, feel different, C + + simplifies the pointer used very comfortable, but C is often more simple rough, really troublesome.

Inverse Polish expression