C/C++ 实现整数四则运算

 问题：实现整数的四则运算（+，-，*，/）

分析：首先把四则运算的字符串转换成后缀表达式（逆波兰式）保存在栈A中，然后获取栈顶元素，如果是数字则保存到另一个栈B中，如果是运算符（+,-,*,/）就从栈B中依次获取栈顶两个操作数进行运算，运算结果再压栈B，如此反复，最终栈B中最后的值就是运算结果。

 

arithmetic.h

#include <stdio.h> #include <malloc.h> #include <string.h> #include <stdlib.h> #include "Stack.h" class Data { public: double num; char op; }; class Arithmetic { private: DoubleStack dStack; //保存四则运算时，后缀表达式中的操作数 CharStack cStack; //保存中缀表达式转换成后缀表达式过程中的操作符 int isp(char op); //栈内优先级 int icp(char op); //栈外优先级 public: Data post[100]; //保存后缀表达式 int curLen; //后缀表达式数组的实际长度 void midTopost(char *c); //把中缀表达式转换成后缀表达式 double calculate(); //进行四则运算 };

 

Stack.h

#include <stdio.h> #include <malloc.h> //栈节点数据结构 class DoubleNode { friend class DoubleStack; private: double value; DoubleNode *next; //构造函数 DoubleNode(double value, DoubleNode *p):value(value),next(p){} }; //栈，用来保存采用后缀表达式进行四则运算时的操作数 class DoubleStack { private: DoubleNode *top; public: DoubleStack():top(NULL){} ~DoubleStack(); void push(double value); double pop(); bool isEmpty(){return top == NULL;} double getTop(); }; //栈节点数据结构 class CharNode { friend class CharStack; private: char value; CharNode *next; //构造函数 CharNode(char value, CharNode *p):value(value),next(p){} }; //栈，用来保存中缀表达式转换成后缀表达式时的运算符 class CharStack { private: CharNode *top; public: CharStack():top(NULL){} ~CharStack(); void push(char value); char pop(); bool isEmpty(){return top == NULL;} char getTop(); void makeEmpty(); };

 

arithmetic.cpp

#include "arithmetic.h" void Arithmetic::midTopost(char *c) { int i = 0; int k; int j; char tmp; char a[100]; char num[10]; //下面开始把字符串中的操作符（+-*/）放入后缀表达式 cStack.makeEmpty(); cStack.push('#'); //字符串最后都加一个# strcat(c, "#"); k = 0; while (c[k] != '/0') { if (c[k] == '+' || c[k] == '-' || c[k] == '*' || c[k] == '/' || c[k] == '(') { //如果优先级低，一直退栈，否则入栈 while (isp(cStack.getTop()) > icp(c[k])) { post[i++].op = cStack.pop(); } cStack.push(c[k]); } else if (c[k] == ')') { //一直退栈到'(' while (isp(cStack.getTop()) >= icp(')')) { tmp = cStack.pop(); if (tmp != '(') { post[i++].op = tmp; } } } else if (c[k] == '#') { while (isp(cStack.getTop()) > icp('#')) { tmp = cStack.pop(); post[i++].op = tmp; } } else if (c[k] >= '0' && c[k] <= '9') { //数字，继续往后获取字符，如果是数字，全部拼装到num中，然后转换成double类型 j = 0; memset(num, 0, 10); num[j] = c[k]; k = k + 1; while (c[k] >= '0' && c[k] <= '9') { num[++j] = c[k]; k++; } post[i].num = atof(num); post[i].op = '#'; i++; k--; } else { //其他非法字符，不处理 } k++; } curLen = i; } //栈内优先级，栈内优先级大于栈外优先级 //'('的栈内优先级应该比所有的操作符都小（除了#） //')'的栈内优先级应该最大 //+-的优先级一致，*/的优先级一致 int Arithmetic::isp(char op) { int pri; switch (op) { case '#' : pri = 0; break; case '(' : pri = 1; break; case '+' : pri = 3; break; case '-' : pri = 3; break; case '*' : pri = 5; break; case '/' : pri = 5; break; case ')' : pri = 10; break; } return pri; } //栈外优先级 int Arithmetic::icp(char op) { int pri; switch (op) { case '#' : pri = 0; break; case '(' : pri = 10; break; case '+' : pri = 2; break; case '-' : pri = 2; break; case '*' : pri = 4; break; case '/' : pri = 4; break; case ')' : pri = 1; break; } return pri; } //根据后缀表达式进行四则运算 double Arithmetic::calculate() { int i; double result = 0; double left, right; for (i = 0; i < curLen; i++) { //如果是数字就入栈 if (post[i].op == '#') { dStack.push(post[i].num); } else //如果是操作符，就取出两个数字进行运算 { right = dStack.pop(); left = dStack.pop(); switch (post[i].op) { case '+' : dStack.push(left + right); break; case '-' : dStack.push(left - right); break; case '*' : dStack.push(left * right); break; case '/' : dStack.push(left / right); break; } } } return dStack.pop(); }

 

Stack.cpp

#include "Stack.h" DoubleStack::~DoubleStack() { DoubleNode *p; while (NULL != top) { p = top; top = top->next; delete p; } } void DoubleStack::push(double value) { top = new DoubleNode(value,top); } double DoubleStack::pop() { if (!isEmpty()) { DoubleNode *p; p = top; top = top->next; double nodeValue = p->value; delete p; return nodeValue; } } double DoubleStack::getTop() { return top->value; } CharStack::~CharStack() { CharNode *p; while (NULL != top) { p = top; top = top->next; delete p; } } void CharStack::push(char value) { top = new CharNode(value,top); } char CharStack::pop() { if (!isEmpty()) { CharNode *p; p = top; top = top->next; char nodeValue = p->value; delete p; return nodeValue; } } void CharStack::makeEmpty() { CharNode *p; while (NULL != top) { p = top; top = top->next; delete p; } } char CharStack::getTop() { return top->value; }

 

main.cpp

#include "arithmetic.h" int main() { char tmp[100]; printf("please input a arithmetic express:/n"); scanf("%s", tmp); Arithmetic ari = Arithmetic(); ari.midTopost(tmp); printf("the result = [%f]/n", ari.calculate()); getchar(); }