خبرگزاری آیصد (جدیدترین و جذاب ترین اخبار ایران و جهان)

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سورس تبدیل infix به postfix  در c++

#include #include #include using namespace std; void Convert(const string & Infix, string & Postfix); bool IsOperand(char ch); bool TakesPrecedence(char OperatorA, char OperatorB); int main(void) { cout<<"www.sitted-boy.blogfa.com"<<' '; char Reply; do { string Infix, Postfix; // local to this loop cout << "Enter an infix expression (e.g. (a+b)/c^2, with no spaces):" << endl; cin >> Infix; Convert(Infix, Postfix); cout << "The equivalent postfix expression is:" << endl << Postfix << endl; cout << endl << "Do another (y/n)? "; cin >> Reply; } while (tolower(Reply) == 'y'); return 0; } /* Given: ch A character. Task: To determine whether ch represents an operand (here understood to be a single letter or digit). Return: In the function name: true, if ch is an operand, false otherwise. */ bool IsOperand(char ch) { if (((ch >= 'a') && (ch <= 'z')) || ((ch >= 'A') && (ch <= 'Z')) || ((ch >= '0') && (ch <= '9'))) return true; else return false; } /* Given: OperatorA A character representing an operator or parenthesis. OperatorB A character representing an operator or parenthesis. Task: To determine whether OperatorA takes precedence over OperatorB. Return: In the function name: true, if OperatorA takes precedence over OperatorB. */ bool TakesPrecedence(char OperatorA, char OperatorB) { if (OperatorA == '(') return false; else if (OperatorB == '(') return false; else if (OperatorB == ')') return true; else if ((OperatorA == '^') && (OperatorB == '^')) return false; else if (OperatorA == '^') return true; else if (OperatorB == '^') return false; else if ((OperatorA == '*') || (OperatorA == '/')) return true; else if ((OperatorB == '*') || (OperatorB == '/')) return false; else return true; } /* Given: Infix A string representing an infix expression (no spaces). Task: To find the postfix equivalent of this expression. Return: Postfix A string holding this postfix equivalent. */ void Convert(const string & Infix, string & Postfix) { stack OperatorStack; char TopSymbol, Symbol; int k; for (k = 0; k < Infix.size(); k++) { Symbol = Infix[k]; if (IsOperand(Symbol)) Postfix = Postfix + Symbol; else { while ((! OperatorStack.empty()) && (TakesPrecedence(OperatorStack.top(), Symbol))) { TopSymbol = OperatorStack.top(); OperatorStack.pop(); Postfix = Postfix + TopSymbol; } if ((! OperatorStack.empty()) && (Symbol == ')')) OperatorStack.pop(); // discard matching ( else OperatorStack.push(Symbol); } } while (! OperatorStack.empty()) { TopSymbol = OperatorStack.top(); OperatorStack.pop(); Postfix = Postfix + TopSymbol; } }