#include #include #include using namespace std; /*栈*/ template class CStack { public: int m_count; T * m_arr; int m_curposition; CStack(int count) { m_arr = new T [count]; m_count = count; m_curposition = -1; } bool push(T val) { if(m_curposition == m_count-1) return false; m_arr[++m_curposition] = val; } T pop() { if(IsEmpty()) return 0; return m_arr[m_curposition--]; } T GetElement() { if(IsEmpty()) return 0; return m_arr[m_curposition]; } bool IsEmpty() { if(m_curposition < 0) return true; return false; } ~CStack() { 

delete [] m_arr; } }; /* 操作函数定义 */ bool ExpressionIsRight(char * pExpression); bool ProcessExpression(char * pExpression); int GetIndex(char ch); void Calculate(); double GetResult(); bool IsEnd(char ch); double GetNum(char *pStr, int & i); CStack stack_sign(100); CStack stack_num(100); // 运算符栈 // 表达式是否正确 // 处理表达式 // 获取操作符在数组中的下标 // 计算 // 得到结果 // 表达式是否结束 // 获取操作数 // 操作数栈 //运算符号优先级表 int PriTbl[7][7]={ {1,1,-1,-1,-1,1,1}, {1,1,-1,-1,-1,1,1}, {1,1,1,1,-1,1,1}, {1,1,1,1,-1,1,1}, {-1,-1,-1,-1,-1,0,2}, {1,1,1,1,2,1,1}, {-1,-1,-1,-1,-1,2,0} }; void main() { char strExpression[100]; cout << "请输入算术表达式(请注意，括号应在英文输入法下输入，否则会出现错误)："; cin >> strExpression; if(!ProcessExpression(strExpression)) // 处理表达式 { cout << "表达式错误！" << endl; } else cout << "计算结果：" << GetResult() << endl; // 输入表达式 // 输出结果 } bool ExpressionIsRight(char * pExpression) { int len = strlen(pExpression); char arr[7] = {'+','-','*','/','(',')','.'}; for(int i=0; i='0' && pExpression[i]<='9')) 

{ if(pExpression[0] == '.' || pExpression[len-1] == '.') return false; int flag = 0; for(int j=0; j= '0' && pExpression[i] <= '9') // 操作数 { double val = GetNum(pExpression, i); stack_num.push(val); } else // 操作符 { int pre = GetIndex(stack_sign.GetElement()); int next = GetIndex(pExpression[i]); switch(PriTbl[pre][next]) { case -1: stack_sign.push(pExpression[i]); break; case 0: // next = pre // next > pre 

if(IsEnd(pExpression[i])) return true; stack_sign.pop(); break; case 1: Calculate(); i--; break; // back // next < pre } } } return true; } double GetNum(char *pStr, int & i) { char Nums[100]; int j = 0; while((pStr[i] >= '0' && pStr[i] <= '9') || pStr[i]=='.') Nums[j++] = pStr[i++]; i--; Nums[j] = '\0'; return atof(Nums); } int GetIndex(char ch) { switch(ch) { case '+': return 0; case '-': return 1; case '*': return 2; case '/': return 3; case '(': return 4; case ')': return 5; case '#': return 6; } } void Calculate() { double num1, num2; num2 = stack_num.pop(); if(stack_num.IsEmpty()) { cout << "表达式错误！" << endl; 

exit(0); } num1 = stack_num.pop(); switch(stack_sign.pop()) { case '+': stack_num.push(num1+num2);return; case '-': stack_num.push(num1-num2);return; case '*': stack_num.push(num1*num2);return; case '/': { if(num2 == 0) { cout << "除数不能为 0！程序终止！" << endl; exit(0); } stack_num.push(num1/num2); return; } } } bool IsEnd(char ch) { if(ch == '#') if(stack_sign.GetElement() == ch) return true; return false; } double GetResult() { if(stack_sign.GetElement() != '#') { cout << "表达式错误！" << endl; exit(0); } return stack_num.GetElement(); }