目前正在学习数据结构，根据书本上的思路自己捣鼓了一个表达式计算的小程序，目前支持负数、小数运算和报错。
下面贴上代码，代码写的很烂（耦合度比较高，比较繁琐），大家如果有什么更好的建议可以提一下！
PS：第一次写博客，诚惶诚恐
#include <stack> #include <iostream> #include <string> //cin>>string #include <cstring> //strcpy_s() #include <math.h> //pow() using namespace std; char ops[] = { '+','-','/','*','(',')','#','.','0','1','2','3','4' ,'5','6','7','8','9' };//符号集 int icp[] = { 2,2,4,4,7,1,0,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1 };//进栈优先级 int isp[] = { 3,3,5,5,1,7,0,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1 };//栈内优先级 class Calculator { public: Calculator(); ~Calculator(); void Run(); private: char* cOrin;//中缀表达式数组 char** cResu;//后缀表达式 void Initialize();//初始化 bool ErrCheck(string expr);//检错 int icpF(char c);//栈外优先级搜索 int ispF(char c);//栈内优先级搜索 void InToPost();//中缀转后缀 double getOperand(int pos);//获取数字 double doOperation(char Operator, double op1, double op2);//计算 }; Calculator::Calculator() { cOrin = NULL; cResu = NULL; } Calculator::~Calculator() { delete[] cOrin; int size = sizeof(*this->cResu) / sizeof(char*); for (int i = 0; i < size; i++) { delete[] this->cResu[i]; } delete[] this->cResu; } void Calculator::Initialize() { string cinOrder = "";//中缀表达式 int size = 0;//表达式长度 while (true) { cout << "请输入表达式："; cin >> cinOrder; size = cinOrder.size(); if (this->ErrCheck(cinOrder) == true) { goto loop; } else { break; } loop: { cinOrder = ""; size=0; continue; } } this->cOrin = new char[size + 2]; this->cResu = new char*[size + 1]; strcpy_s(this->cOrin, size+1, cinOrder.c_str()); this->cOrin[size] = '#';//标识表达式结束 this->cOrin[size + 1] = '\0';//标识数组结束 } bool Calculator::ErrCheck(string expr){ int rBrace = 0;//右括号计数 int lBrace = 0;//左括号计数 bool isInvaild = false;//非法输入 bool isDefalut = false;//括号不匹配 for (int count = 0; count < expr.size(); count++) { if (expr[count] == '(') { lBrace++; } else if (expr[count] == ')') { rBrace++; } if (this->icpF(expr[count]) == -2) { isInvaild = true; } } if (lBrace != rBrace) { isDefalut = true; } if (isInvaild == true) { cout << "表达式含有非法字符，请检查！\n"; } if (isDefalut == true) { cout << "表达式左右括号不匹配，请检查！\n"; } if (isInvaild == true || isDefalut == true) { return true; } else { return false; } } void Calculator::Run() { int count = 0; int search; double op1, op2, number; this->Initialize(); this->InToPost(); stack<double> s; while (this->cResu[count][0] != '#') { search = this->icpF(this->cResu[count][0]); if (search == -1) { number = this->getOperand(count); s.push(number); } else { op2 = s.top();//后进先出 s.pop(); op1 = s.top(); s.pop(); number=this->doOperation(this->cResu[count][0], op1, op2); s.push(number); } count++; } number = s.top(); s.pop(); cout << "结果为：" << number << endl; } double Calculator::doOperation(char Operator, double op1, double op2) { double number = 0; switch (Operator) { case '+': number = op1 + op2; break; case '-': number = op1 - op2; break; case '*': number = op1*op2; break; case '/': number = op1 / op2; break; } return number; } double Calculator::getOperand(int pos) { double total = 0.0;//实际数字 bool isDec = false;//判断是否小数 int intCount = 0;//整数计数 int count = 0;//数组遍历计数 int numBit = 0;//每位上的数字 int i = 0;//小数次方计数 while (this->cResu[pos][count] != '+' && this->cResu[pos][count] != '-') { if (this->cResu[pos][count] == '.') { isDec = true; break; } else { intCount++; count++; } } while (this->cResu[pos][count] != '+' && this->cResu[pos][count] != '-') {//当遇到小数时，将计数移到符号位上 count++; } if (this->cResu[pos][count] == '+') {//正数 count = 0; if (isDec == true) {//是小数 while (this->cResu[pos][count] != '.') { numBit = this->cResu[pos][count++] - '0'; total += numBit*pow(10, --intCount); } count++;//跳过小数点 while (this->cResu[pos][count] != '+') { numBit = this->cResu[pos][count++] - '0'; total += numBit*pow(10, --i); } } else {//不是小数 while (this->cResu[pos][count] != '+') { numBit = this->cResu[pos][count++] - '0'; total += numBit*pow(10, --intCount); } } } else {//负数 count = 0; if (isDec == true) {//是小数 while (this->cResu[pos][count] != '.') { numBit = this->cResu[pos][count++] - '0'; total += numBit*pow(10, --intCount); } count++;//跳过小数点 while (this->cResu[pos][count] != '-') { numBit = this->cResu[pos][count++] - '0'; total += numBit*pow(10, --i); } total = -total; } else {//不是小数 while (this->cResu[pos][count] != '-') { numBit = this->cResu[pos][count++] - '0'; total += numBit*pow(10, --intCount); } total = -total; } } return total; } int Calculator::icpF(char c) { int j = -2; for (int i = 0; i < 18; i++) { if (ops[i] == c) { j = icp[i]; } } return j; } int Calculator::ispF(char c) { int j = -2; for (int i = 0; i < 18; i++) { if (ops[i] == c) { j = isp[i]; } } return j; } void Calculator::InToPost() { bool isDec = false;//判断是否为小数 bool isNeg = false;//判断是否为负数 int cInCount = 0;//中缀表达式计数 int cPostCount = 0;//后缀表达式计数 int nCount = 0;//数字位数计数 char c = '\0'; int i;//优先级 int temp;//重置中缀表达式计数 stack<char> s; s.push('#');//确保扫描到的第一个运算符进栈 while (true) { c = this->cOrin[cInCount];//扫描中缀表达式 i = this->icpF(c); if (i == -1) {//没扫到运算符 temp = cInCount; while ((i = this->icpF(this->cOrin[cInCount])) == -1) {//确定数字位数 if (this->cOrin[cInCount] == '.') {//遇到小数点 isDec = true; cInCount++; } else { nCount++; cInCount++; } } if (isNeg == false) {//如果不是负数 if (isDec == true) { this->cResu[cPostCount] = new char[nCount + 3];//存放小数点、正号和'\0' for (int j = 0; j < nCount + 1; j++, temp++) {//输出数字 this->cResu[cPostCount][j] = this->cOrin[temp]; } this->cResu[cPostCount][nCount + 1] = '+'; this->cResu[cPostCount][nCount + 2] = '\0'; isDec = false;//重置小数布尔值 } else { this->cResu[cPostCount] = new char[nCount + 2];//存放正号和'\0' for (int j = 0; j < nCount; j++, temp++) {//输出数字 this->cResu[cPostCount][j] = this->cOrin[temp]; } this->cResu[cPostCount][nCount] = '+'; this->cResu[cPostCount][nCount + 1] = '\0'; } } else {//如果是负数 if (isDec == true) { this->cResu[cPostCount] = new char[nCount + 3];//存放小数点、负号和'\0' for (int j = 0; j < nCount + 1; j++, temp++) {//输出数字 this->cResu[cPostCount][j] = this->cOrin[temp]; } this->cResu[cPostCount][nCount + 1] = '-'; this->cResu[cPostCount][nCount + 2] = '\0'; cPostCount++; isDec = false;//重置小数布尔值 } else { this->cResu[cPostCount] = new char[nCount + 2];//存放负号和'\0' for (int j = 0; j < nCount; j++, temp++) {//输出数字 this->cResu[cPostCount][j] = this->cOrin[temp]; } this->cResu[cPostCount][nCount] = '-'; this->cResu[cPostCount][nCount + 1] = '\0'; } isNeg = false;//重置负数布尔值 } cPostCount++; nCount = 0; } else {//扫描到运算符 if (c == ')') { while (s.top() != '(') {//连续输出直到遇到'(' this->cResu[cPostCount] = new char[1]; this->cResu[cPostCount][0] = s.top(); s.pop(); cPostCount++; } s.pop();//'('直接出栈不输出 cInCount++; } else if (this->cOrin[cInCount] == '-' && cInCount == 0) {//表达式例子：-4+5# isNeg = true; cInCount++;//跳过负号 continue; } else if (this->cOrin[cInCount] == '-' && cInCount > 0 && this->cOrin[cInCount - 1] != ')' && this->icpF(this->cOrin[cInCount - 1]) != -1) {//表达式例子：((-4+5)+1)*3# isNeg = true; cInCount++;//跳过负号 continue; } else if (i <= ispF(s.top())) {//进栈优先级小于栈内优先级，一直输出 while (i <= this->ispF(s.top())) { this->cResu[cPostCount] = new char[1]; this->cResu[cPostCount][0] = s.top(); s.pop(); if (s.empty() == true) { goto exit;//当遇到中缀表达式的#时，一直输出到栈空然后退出函数 } cPostCount++; } } else {//进栈优先级大于栈内优先级，入栈 s.push(c); cInCount++; } } } exit: return; } int main() { Calculator c1; c1.Run(); system("pause"); return 0; }