逆波兰计算器

逆波兰计算器

所谓的逆波兰计算器，就是将我们常见的中缀表达式，转换为后缀表达式，来供计算机运算的计算器。
适合栈刚入门做练习

#include <iostream>
#include <cstdlib>
#include <cctype>
using namespace std;

const int MaxSize = 30;
const int Stack_Init_Size = 30;
const int StackIncrement = 10;

typedef char ElemType_c;
typedef double ElemType_d;
typedef struct{
	ElemType_c *top;
	ElemType_c *base;
	int StackSize;
}sqStack_c;
typedef struct{
	ElemType_d *top;
	ElemType_d *base;
	int StackSize;
}sqStack_d;

bool InitStack_c(sqStack_c *s);
bool InitStack_d(sqStack_d *s);
void Push_c(sqStack_c *s,ElemType_c e);
void Push_d(sqStack_d *s,ElemType_d e);
void Pop_c(sqStack_c *s,ElemType_c *e);
void Pop_d(sqStack_d *s,ElemType_d *e);
int LenStack_c(sqStack_c s);
int LenStack_d(sqStack_d s);

int main()
{
	sqStack_c s;
	InitStack_c(&s);
	ElemType_c c,e;
	ElemType_c arr[MaxSize];
	int i = 0;
	cout << "Please enter the infix expression(# to stop): ";
	cin >> c;
	while('#' != c){
		while(isdigit(c) || '.' == c){
			arr[i++] = c;
			arr[i] = '\0';
			cin >> c;
			if(!(isdigit(c) || '.' == c))
			{
				arr[i++] = ' ';
				arr[i] ='\0';
			}
		}
		if(')' == c)
		{
			Pop_c(&s,&e);
			while('(' != e){
				arr[i++] = e;
				arr[i++] = ' ';
				arr[i] = '\0';
				Pop_c(&s,&e);
			}
		}
		else if('+' == c || '-' == c)
		{
			if(!LenStack_c(s))
				Push_c(&s,c);
			else
			{
				do{
					Pop_c(&s,&e);
					if('(' == e)
						Push_c(&s,e);
					else
					{
						arr[i++] = e;
						arr[i++] = ' ';
						arr[i] = '\0';
					}
				}while('(' != e && LenStack_c(s));
				Push_c(&s,c);
			}
		}
		else if('*' == c || '/' == c || '(' == c)
		{
			Push_c(&s,c);
		}
		else if('#' == c)
		{
			break;
		}
		else
		{
			cerr << "Enter Error.\n";
			break;
		}
		cin >> c;
	}
	while(LenStack_c(s)){
		Pop_c(&s,&e);
		arr[i++] = e;
		arr[i++] = ' ';
		arr[i] = '\0';
	}
	arr[i-1] = '#';
	
	// calc
	sqStack_d calc;
	InitStack_d(&calc);
	ElemType_d d,f;
	int j = 0, k = 0;
	char str[MaxSize];
	char oop = arr[j++];
	while('#' != oop){
		while(isdigit(oop) || '.' == oop){
			str[k++] = oop;
			str[k] = '\0';
			if(k >= MaxSize)
			{
				cerr << "Runout.\n";
				return -1;
			}
			oop = arr[j++];
			if(' ' == oop)
			{
				d = atof(str);
				Push_d(&calc,d);
				k = 0;
				break;
			}
		}
		switch(oop){
			case '+':	Pop_d(&calc,&d);
						Pop_d(&calc,&f);
						Push_d(&calc,f+d); break;
			case '-':	Pop_d(&calc,&d);
						Pop_d(&calc,&f);
						Push_d(&calc,f-d); break;
			case '*':	Pop_d(&calc,&d);
						Pop_d(&calc,&f);
						Push_d(&calc,f*d); break;
			case '/':	Pop_d(&calc,&d);
						Pop_d(&calc,&f);
						Push_d(&calc,f/d); break;
		}
		oop = arr[j++];
	}
	Pop_d(&calc,&d);
	cout.setf(ios_base::fixed);
	cout.setf(ios::showpoint);
	cout.precision(4);
	cout << "The final result is: " << d;
	return 0;
}

bool InitStack_c(sqStack_c *s)
{
	s->base = (ElemType_c *)malloc(Stack_Init_Size * sizeof(ElemType_c));
	if(!s->base)
		return false;
	s->top = s->base;
	s->StackSize = Stack_Init_Size;
	return true;
}

bool InitStack_d(sqStack_d *s)
{
	s->base = (ElemType_d *)malloc(Stack_Init_Size * sizeof(ElemType_d));
	if(!s->base)
		return false;
	s->top = s->base;
	s->StackSize = Stack_Init_Size;
	return true;
}

void Push_c(sqStack_c *s,ElemType_c e)
{
	if(s->top - s->base >= s->StackSize)
	{
		s->base = (ElemType_c *)realloc(s->base,(s->StackSize + StackIncrement) * sizeof(ElemType_c));
		if(!s->base)
			exit(EXIT_FAILURE);
		s->top = s->base + s->StackSize;
		s->StackSize = s->StackSize +StackIncrement;
	}
	*(s->top) = e;
	s->top++;
}

void Push_d(sqStack_d *s,ElemType_d e)
{
	if(s->top - s->base >= s->StackSize)
	{
		s->base = (ElemType_d *)realloc(s->base,(s->StackSize + StackIncrement) * sizeof(ElemType_d));
		if(!s->base)
			exit(EXIT_FAILURE);
		s->top = s->base + s->StackSize;
		s->StackSize = s->StackSize + StackIncrement;
	}
	*(s->top) = e;
	s->top++;
}

void Pop_c(sqStack_c *s,ElemType_c *e)
{
	if(s->top == s->base)
		return;
	*e = *--(s->top);
}

void Pop_d(sqStack_d *s,ElemType_d *e)
{
	if(s->top == s->base)
		return;
	*e = *--(s->top);
}

int LenStack_c(sqStack_c s)
{
	if(s.top == s.base)
		return 0;
	return s.top - s.base;
}

int LenStack_d(sqStack_d s)
{
	if(s.top == s.base)
		return 0;
	return s.top - s.base;
}

本文地址：https://blog.csdn.net/weixin_45677702/article/details/108155696