c - 我在代码块中编写的堆栈实现代码编译成功，但在运行时显示错误

Question

我附上了运行时错误的屏幕截图。

此代码将创建一个堆栈

#include <stdio.h>
#include <stdlib.h>
#define SIZE 5         
// Declared a Structure with top,an array as its members

     struct Stack {  
     int items[SIZE],top;  

     };


//push method inserts an element in the stack

void push(struct Stack *s1,int x){   
    s1->items[++s1->top]=x;
}

// pop  method is for Removing the Elements

void pop(struct Stack* s1){  
    printf("Before pop the Top is %d ",s1->top);
    int a=s1->items[s1->top--];
    printf("After pop the Top is %d",s1->top);
}


//Main method


void main() {
    struct Stack s,*s1;
    struct Stack top = {-1};    //Initializing Top variable in Structure 
    int n;

    //loop to insert the elements

     for(int i=0;i<SIZE;i++){
     printf("Enter the elements to be pushed");
     scanf("%d",&n);
     push( s1, n);
      }
    pop(s1);
    pop(s1);

    printf("The Elements of the Stack after performing all the operations are   ");

    // Print the elements of the stack

    for(int i=0;i<SIZE;i++) {  
     printf("%d",s1->items[SIZE]); 

    }

}

Answer 1

有很多问题:

这是您的程序的修正版本。所有更正均已发表评论。 代码仍然很草率(例如，没有错误检查，变量名称毫无意义)，但至少它可以工作。

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

#define SIZE 5         

struct Stack {
  int items[SIZE];
  int top;             // better readability
};


// push method inserts an element in the stack

void push(struct Stack *s1, int x) {
  s1->items[++s1->top] = x;
}

// pop  method is for removing ONE Element  // COMMENT CORRECTED

int pop(struct Stack* s1) {   // we need to return the popped element
  printf("Before pop the Top is %d\n", s1->top);
  int a = s1->items[s1->top--];
  printf("After pop the Top is %d\n", s1->top);
  return a;
}


int main() {        // main must return an int
  struct Stack s;   // removed useless s1 ansd top variables
                    // BTW s1 was an uninitialized pointer so this was
                    // totally wrong
  int n;

  s.top = -1;       // initialize top correctly 
                    // struct Stack s = {-1}  will not initialize s.top !!

  for (int i = 0; i<SIZE; i++) {
    printf("Enter the elements to be pushed: ");
    scanf("%d", &n);
    push(&s, n);
  }

  printf("First popped value: %d\n", pop(&s));   // print popped elements
  printf("Second popped value: %d\n", pop(&s));

  printf("The Elements of the Stack after performing all the operations are: ");

  for (int i = 0; i <= s.top; i++) {   //i <= top instead of i < SIZE
    printf("%d\n", s.items[i]);        // s.items[i] instead of s.items[SIZE]
  }
}