栈的应用之中缀表达式求值（QT平台）

#include <Expression.h> #include <QStack> #include <cstring> double Expression::Operate(){ for(int i=0;i<statement.length();i++) { char ch =statement[i]; switch(ch) { case '+': case '-': { if(!operation.empty()&&operation.top()!='(') Calculate(); operation.push(ch); break; } case '*': case '/': { if(!operation.empty()&&(operation.top()=='*'||operation.top()=='/')) Calculate(); operation.push(ch); break; } case '(': operation.push(ch); break; case ')': while(operation.top()!='(') Calculate(); operation.pop(); break; default: { int number=0; while(statement[i]>='0'&&statement[i]<='9') { number= number*10+statement[i]-'0'; i++; } operato.push(number); i--; } } } while(!operation.empty()) Calculate(); double result = operato.top(); return result; } void Expression::Calculate(){ char op; int op1,op2; op2=operato.pop(); op1=operato.pop(); op =operation.pop(); int temp = 0; switch(op){ case '+': temp = op1 + op2; break; case '-': temp = op1 - op2; break; case '*': temp = op1 * op2; break; case '/': temp = op1 / op2; break; } operato.push(temp); }