编程计算表达式:6 5 2 3 + 8 * + 3 + * 的结果

计算表达式:6 5 2 3 + 8 * + 3 + * 

算法思路：

               使用栈，当见到一个数时就把它推入栈中;在遇到一个运算符时该运算符就作用于从该栈弹出的两个数上，将所得结果推入栈中。

stack.h

#ifndef STACK_H_
#define STACK_H_

struct StackRecord;
typedef struct StackRecord * STACK;
typedef int ElementType;

struct StackRecord
{
	int Capacity;
	int TopOfStack;
	ElementType * array;
};

int IsEmpty(STACK S);
int IsFull(STACK S);
STACK CreateStack(int MaxElements);
void DisposeStack(STACK S);
void MakeEmpty(STACK S);
void Push(ElementType X,STACK S);
ElementType Top(STACK S);
void Pop(STACK S);
ElementType TopAndPop(STACK S);

#endif

#define EmptyTOS (-1)
#define MinStackSize (5)

stack.c

#include <stdio.h>
#include <stdlib.h>
#include "stack.h"

STACK CreateStack(int MaxElements)
{
	STACK S;

	if(MaxElements<MinStackSize)
	{
		puts("栈的大小太小");
		exit(1);
	}

	S=(STACK)malloc(sizeof(struct StackRecord));
	if(S==NULL)
	{
		puts("内存不足");
		exit(1);
	}

	S->array=(ElementType *)malloc(sizeof(ElementType)*MaxElements);
	if(S->array==NULL)
	{
		puts("内存不足");
		exit(1);
	}
	S->Capacity=MaxElements;
	MakeEmpty(S);
	
	return S;
}

void DisposeStack(STACK S)
{
	if(S!=NULL)
	{
		free(S->array);
		free(S);
	}
}

int IsEmpty(STACK S)
{
	return S->TopOfStack==EmptyTOS;
}

int IsFull(STACK S)
{
	return S->TopOfStack==S->Capacity;
}

void MakeEmpty(STACK S)
{
	S->TopOfStack=EmptyTOS;
}

void Push(ElementType X,STACK S)
{
	if(IsFull(S))
	{
		puts("栈满了");
		exit(1);
	}
	else
		S->array[++S->TopOfStack]=X;
}

ElementType Top(STACK S)
{
	if(!IsEmpty(S))
		return S->array[S->TopOfStack];
	puts("空栈");
	return 0;
}

void Pop(STACK S)
{
	if(IsEmpty(S))
	{
		puts("空栈");
		exit(1);
	}
	else
		S->TopOfStack--;
}

ElementType TopAndPop(STACK S)
{
	if(!IsEmpty(S))
		return S->array[S->TopOfStack--];
	puts("空栈");
	return 0;
}

suffix.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "stack.h"
#define LEN 10
#define MAXSTACK 100

int main(void)
{
	STACK stack;
	char str[LEN];
	char symbol;
	int element1,element2,element3;
	
	const char STRING[]="+-*/";
	int x;

	//创建栈
	stack=CreateStack(MAXSTACK);

	//判断空栈
	if(IsEmpty(stack))
		printf("空栈\n");

	printf("输入表达式 ( q 字符 退出): \n");
	while(scanf("%s",str)==1 && str[0]!='q')
	{
		if(strstr(STRING,str))
		{
			symbol=str[0];
			switch(symbol)
			{
				case '+' :
					if(IsEmpty(stack))
					{
						printf("先输入数字\n");
						exit(1);
					}
					else
					{
					element1=TopAndPop(stack);
					element2=TopAndPop(stack);
					element3=element1+element2;
					Push(element3,stack);
					break;
					}
				case '-' :
					if(IsEmpty(stack))
					{
						printf("先输入数字\n");
						exit(1);
					}
					else
					{
					element1=TopAndPop(stack);
					element2=TopAndPop(stack);
					element3=element1-element2;
					Push(element3,stack);
					break;
					}
				case '*' :
					if(IsEmpty(stack))
					{
						printf("先输入数字\n");
						exit(1);
					}
					else
					{
					element1=TopAndPop(stack);
					element2=TopAndPop(stack);
					element3=element1*element2;
					printf("element3 %d\n",element3);
					Push(element3,stack);
					break;
					}
				case '/' :
					if(IsEmpty(stack))
					{
						printf("先输入数字\n");
						exit(1);
					}
					else
					{
					element1=TopAndPop(stack);
					element2=TopAndPop(stack);
					element3=element1/element2;
					Push(element3,stack);
					break;
					}
			}
		}
		else
		{	x=atoi(str);
			Push(x,stack);
		}
	}
	
	//显示栈
	printf("表达式的结果为:");
	for(int i=0;i<=stack->TopOfStack;i++)
		printf("%d",stack->array[i]);
	putchar('\n');
	
	return 0;
}