C语言实现栈应用：后缀表达式

代码

#include <stdio.h>
#include<stdlib.h>
#include<string.h>
 #include <ctype.h>
struct StackRecord
{
    
    
    int Capacity;
    int TopOfStack;
    int *Array;
    
};

typedef struct StackRecord *Stack;
Stack CreateStack(int MaxElem)
{
    
    
    Stack S;
    S=(StackRecord *)malloc(sizeof(struct StackRecord));
    if(S==NULL)
        printf("Out of space!1");
    S->Array=(int *)malloc(sizeof(int)*MaxElem);
    if(S->Array==NULL)
        printf("Out of space!2");
    S->Capacity=MaxElem;
    S->TopOfStack=-1;
    return S;
}
void DisposeStack(Stack S)
{
    
    
    if(S!=NULL)
    {
    
    
        free(S->Array);
        free(S);
    }
}
int IsEmpty(Stack S)
{
    
    
    return S->TopOfStack==-1;
}
int IsFull(Stack S)
{
    
    
    return S->TopOfStack==S->Capacity-1;
}
void Push(Stack S,int x)
{
    
    
    if(IsFull(S))
        printf("Out of space!3");
    else 
        S->Array[++S->TopOfStack]=x;
}
int Top(Stack S)
{
    
    
    if(IsEmpty(S))
    {
    
    
        printf("Empty Stack!");return 0;
    }
    else
        return S->Array[S->TopOfStack];
        
}
void Pop(Stack S)
{
    
    
    if(IsEmpty(S))
        printf("Empty Stack!");
    else
        S->TopOfStack--;
}
int main(void) {
    
     
    char str[100];
    int num1,num2,sum;
    scanf("%s",str);
    int length=strlen(str);
    Stack S=CreateStack(length+1);
    for (int i=0;i<length;i++)
    {
    
    
        if(isdigit(str[i]))
        {
    
    
            int d=str[i]- '0';
            Push(S,d);
        }
        else if(str[i]=='+')
        {
    
    
            num1=Top(S);
            Pop(S);
            num2=Top(S);
            Pop(S);
            sum=(num1+num2);
            Push(S,sum);
        }
            
        else if(str[i]=='-')
        {
    
    
            num1=Top(S);
            Pop(S);
            num2=Top(S);
            Pop(S);
            sum=(num1-num2);
            Push(S,sum);
        }
        else if(str[i]=='*')
        {
    
    
            num1=Top(S);
            Pop(S);
            num2=Top(S);
            Pop(S);
            sum=(num1*num2);
            Push(S,sum);
        }
        else if(str[i]=='/')
        {
    
    
            num1=Top(S);
            Pop(S);
            num2=Top(S);
            Pop(S);
            sum=(num1/num2);
            Push(S,sum);
        }    
    }
    printf("%d",Top(S));
   
}

输入：1234-*+42/-
输出：-3