suffix expression (inverse Polish expression) and evaluated
This is a simple application of a stack.
Rules: From left to right to traverse infix expression of each number and symbol, if the number on the output, that is, as part of the suffix expression;
If the symbol, then the top of the stack to determine the priority of the symbol, is the right bracket or priority lower than the top sign (multiplication and division priority plus minus) then the top of the stack elements out to find and output, and the current symbol into the stack, until the final output suffix expression.
Support (), + 、-、 *,/and%
#include <stdexcept> #include <iostream> #include <vector> #include <string> #include <stack
> #include <regex> #include <cmath> using namespace std;
Split character Vector<string> split () {vector<string> temp_vecstr;
Regex Reg_dig ("[[:d Igit:].]");
String Temp_str, Temp_str1, TEMP_STR2, TEMP_STR3;
cout << "Please enter an expression:" << Endl;
Cin >> Temp_str;
for (Auto i = Temp_str.begin (); I!= temp_str.end (); ++i) {temp_str2 = *i;
if (Regex_search (TEMP_STR2, Reg_dig)) {temp_str1 = = TEMP_STR2;
Auto P = i;
if (++p = = Temp_str.end ()) {temp_vecstr.push_back (TEMP_STR1);
Temp_str1.clear ();
}--p;
if (++p!= temp_str.end ()) {--p;
TEMP_STR2 = * (++p);
if (!regex_search (TEMP_STR2, Reg_dig)) {temp_vecstr.push_back (TEMP_STR1); Temp_str1.clear (); }} else {if (temp_str2 = "+" | | temp_str2 = = "| | temp_str2 = =" * "| | temp_ STR2 = = "/" | | TEMP_STR2 = "(" | |
TEMP_STR2 = = "%") {temp_vecstr.push_back (TEMP_STR2);
Auto P = i;
if (++p!= temp_str.end ()) {--p;
TEMP_STR3 = * (++p);
if (TEMP_STR3 = = "-") {temp_str1 + = TEMP_STR3;
if (++p!= temp_str.end ()) {auto P1 = p;
TEMP_STR3 = *P1; for (; Regex_search (TEMP_STR3, reg_dig) && p1!= temp_str.end (); ++p1, ++i) {Temp
_STR3 = *P1;
if (Regex_search (TEMP_STR3, Reg_dig)) {temp_str1 = = TEMP_STR3;
} } temp_vecstr.push_back (TEMP_STR1);
Temp_str1.clear ();
if (Regex_search (TEMP_STR3, Reg_dig)) {++i; else {Temp_}}}}
Vecstr.push_back (TEMP_STR2);
}} return temp_vecstr; }//Convert to suffix expression stack<string> postfix_expression (vector<string> temp_vecstr) {stack<string> Temp_Stac
Ksymbol, Temp_stackexp, Temp_stack1, Temp_stack2; Regex Reg_dig ("[[:d Igit:].]
+");
String Temp_str;
for (auto &i:temp_vecstr) {temp_str = i;
if (Regex_search (Temp_str, Reg_dig)) {Temp_stackexp.push (TEMP_STR);
} if (Temp_str = = "(") {Temp_stacksymbol.push (TEMP_STR); } if (temp_str = ")") {while TEMP_STACKSYMBOl.top ()!= "(") {Temp_stackexp.push (Temp_stacksymbol.top ());
Temp_stacksymbol.pop ();
} temp_stacksymbol.pop (); } if (Temp_str = = "+" | | | temp_str = = "-") {if (!temp_stacksymbol.empty ()) {if (temp _stacksymbol.top () = = "+" | | Temp_stacksymbol.top () = = "-" | | Temp_stacksymbol.top () = = "*" | | Temp_stacksymbol.top () = = "/" | | Temp_stacksymbol.top () = = "%") {while (!temp_stacksymbol.empty () && temp_stacksymbol.top ()!=
"(") {Temp_stackexp.push (Temp_stacksymbol.top ());
Temp_stacksymbol.pop ();
} temp_stacksymbol.push (TEMP_STR);
else {Temp_stacksymbol.push (TEMP_STR);
} else {Temp_stacksymbol.push (TEMP_STR);
} if (temp_str = "%") { if (!temp_stacksymbol.empty ()) {if (temp_stacksymbol.top () = "*" | | temp_stacksymbol.top () = = "/" || Temp_stacksymbol.top () = = "%") {while (!temp_stacksymbol.empty () && temp_stacksymbol.top ()!= "(" && temp_stacksymbol.top ()!= "+" && temp_stacksymbol.top ()!= "-") {Temp_sta
Ckexp.push (Temp_stacksymbol.top ());
Temp_stacksymbol.pop ();
} temp_stacksymbol.push (TEMP_STR);
else {Temp_stacksymbol.push (TEMP_STR);
} else {Temp_stacksymbol.push (TEMP_STR);
} if (temp_str = "*" | | temp_str = = "/") {if (!temp_stacksymbol.empty ()) { if (temp_stacksymbol.top () = "*" | | temp_stacksymbol.top () = = "/") {while!temp_stacksymbol.empty () && Temp_stacksymbol.top ()!= "(" && temp_stacksymbol.top ()!= "+" && temp_stacksymbol.top ()!= "-") {
Temp_stackexp.push (Temp_stacksymbol.top ());
Temp_stacksymbol.pop ();
} temp_stacksymbol.push (TEMP_STR);
else {Temp_stacksymbol.push (TEMP_STR);
} else {Temp_stacksymbol.push (TEMP_STR);
}} while (!temp_stacksymbol.empty ()) {Temp_stackexp.push (Temp_stacksymbol.top ());
Temp_stacksymbol.pop ();
while (!temp_stackexp.empty ()) {Temp_stack1.push (Temp_stackexp.top ());
Temp_stack2.push (Temp_stackexp.top ());
Temp_stackexp.pop ();
cout << endl << "The suffix expression is:" << Endl << Endl;
while (!temp_stack2.empty ()) {cout << temp_stack2.top () << ""; temp_sTack2.pop ();
} cout << Endl << Endl;
return temp_stack1;
}//Evaluation void Evaluation (Stack<string> temp_stackexp) {Auto Temp_num1 = 0.0, temp_num2 = 0.0; Regex Reg_dig ("[[:d Igit:].]
+");
Stack<double> Temp_stacknum;
String Temp_str;
try {while (!temp_stackexp.empty ()) {temp_str = Temp_stackexp.top ();
if (Regex_search (Temp_str, Reg_dig)) {Temp_stacknum.push (Stod (TEMP_STR));
Temp_stackexp.pop (); } if (Temp_str = = "+") {if (!temp_stacknum.empty ()) {temp_num1 = temp_s
Tacknum.top ();
Temp_stacknum.pop ();
temp_num2 = Temp_stacknum.top ();
Temp_stacknum.pop ();
Temp_stacknum.push (temp_num1 + temp_num2);
Temp_stackexp.pop (); } else {throw runtime_error (expression input error, please reInput! ");}}
if (Temp_str = = "-") {if (!temp_stacknum.empty ()) {temp_num1 = Temp_stacknum.top ();
Temp_stacknum.pop ();
temp_num2 = Temp_stacknum.top ();
Temp_stacknum.pop ();
Temp_stacknum.push (TEMP_NUM2-TEMP_NUM1);
Temp_stackexp.pop ();
else {throw runtime_error ("Input error, please re-enter!"); } if (temp_str = "%") {if (!temp_stacknum.empty ()) {Temp
_NUM1 = Temp_stacknum.top ();
Temp_stacknum.pop ();
temp_num2 = Temp_stacknum.top ();
Temp_stacknum.pop ();
Temp_stacknum.push (Fmod (temp_num2, temp_num1));
Temp_stackexp.pop (); else {throw runtime_eRror ("Input error, please re-enter!"); } if (temp_str = = "*") {if (!temp_stacknum.empty ()) {Temp
_NUM1 = Temp_stacknum.top ();
Temp_stacknum.pop ();
temp_num2 = Temp_stacknum.top ();
Temp_stacknum.pop ();
Temp_stacknum.push (TEMP_NUM1 * temp_num2);
Temp_stackexp.pop ();
else {throw runtime_error ("Input error, please re-enter!"); } if (Temp_str = = "/") {if (!temp_stacknum.empty ()) {Temp
_NUM1 = Temp_stacknum.top ();
Temp_stacknum.pop ();
temp_num2 = Temp_stacknum.top ();
Temp_stacknum.pop ();
Temp_stacknum.push (TEMP_NUM2/TEMP_NUM1);
Temp_stackexp.pop (); else {THRow runtime_error ("Input error, please re-enter!");
catch (Runtime_error &err) {cout << err.what () << Endl;
Return Evaluation (Postfix_expression (Split ()));
The value of the cout << expression is: "<< temp_stacknum.top () << Endl << Endl;}
int main () {while (1) {Evaluation postfix_expression (Split ()));
return 0; }