我被要求使用链表实现堆栈。程序声明两个“堆栈”并使用它们来排序存储在文件中的一些整数。我有以下程序在开始时崩溃。我认为它在第一次崩溃时崩溃了。 （对于文件，用户输入其名称）
/************************************************************************************************************************
Input File: A text file named: "Numbers.txt" that contains integers in random order. These integers are seperated
by either a space or a new line. This file is very essencial for the program to work, because from it the
program gets the integers. below is an example of the file format: (Note that there is a new line after
the last integer in order for the file to be read correctly).
2 1 3 5 4
7 6 8 9
Output File: None
Description: This program reads integers in random order. These integers are sorted by the end of the program's execution.
The sorting operations, using Push and Pop functions are managed by two structures of type stack_t.
The first structure is the main one that will be shown to the user, the second one is the one that holds the
unsorted integers while sorting. By the end stack2 will be empty and stack 1 will be sorted.
*************************************************************************************************************************/
#include <stdio.h>
#define MAXSTACK 10 // Defining the size of the stack as being 10 elements
typedef struct node s_Node;
struct node {
int element;
s_Node*next;
}; // Define the node_t structure with the element of the node and the pointer to the next node
typedef struct{
s_Node *top_stack;
}stack_t; // Define the stack_t structure with a pointer to s_Node (the first element of the linked list)
/*-------------------------- NEEDED PROTOTYPES --------------------------*/
// Initializes a new stack and returns it
stack_t NewStack();
// Returns 1 if the stack is empty, 0 otherwise
int Empty(stack_t q);
// Returns 1 if the stack is full, 0 otherwise
int Full(stack_t q);
// Pushes the element e in the stack. Returns 1 if it could Push.
int Push(int e, stack_t *q);
// Pops an element, placing it in e. Returns 1 if it could Pop.
int Pop(int *e, stack_t *q);
// Search for the top element in the stack and returns it.
int Peek (stack_t s);
// Displays the content of the stack.
void Printstack(const stack_t );
/*============================ MAIN PROGRAM ============================*/
main () {
char filename [20];
int newint, val1, val2;
FILE *file;
stack_t stack1;
stack_t stack2;
stack1=NewStack(); //Initializing the stack
stack2=NewStack();
printf ("\n\tPlease Enter the name of the file that contains your integers: ");
scanf ("%s", &filename);
file = fopen (filename, "r");
if (file!=NULL) {
fscanf (file, "%d", &newint);
while (!feof (file)&&!Full (stack1))
{
if ( Empty (stack1)) // Putting the first integer read from the file into the first stack.
{
Push (newint, &stack1);
}
else if (newint <= Peek(stack1)) //If the integer read from the file is less or equal to the integer in the top of the stack
{
Push(newint, &stack1); // Push the integer into stack1.
}
else
{
while ( newint > Peek (stack1) )
{ //Repeat poping from stack1 and pushing into stack2
// until it the integer read from the file is bigger than the top element of stack1
printf ("gOT into THE WHILE LOOP\n");
Pop (&val1,&stack1);
Push (val1, &stack2);
Printstack (stack2);
}
printf ("gOT OUT OF THE WHILE LOOP\n");
Push (newint, &stack1); //Pushing the integer read from the file into the first stack.
Printstack (stack1);
while (!Empty(stack2))
{ // Keep poping elements from stack2 and pushing them into stack1 until stack2 is empty
Pop (&val2,&stack2);
Push (val2, &stack1);
}
}
fscanf (file, "%d", &newint);
} // End while
if (feof(file)) printf ("\n\tYou have reached the end of the file: %s.\n\tThere are no more elements to read.",filename);
else printf ("\n\n\tYour stack is full.\n\tYou can not enstack more elemeents");
fclose (file);
printf ("\nThe final result");
Printstack (stack1);
}else printf ("Error!!! Your file did not open successefully!\n"); // Error checking in reading the file
} // End main
/*-------------------------- FUNCTION DEFINITIONS --------------------------*/
// Initializes a new stack and returns it
stack_t NewStack()
{
stack_t *n_stack;
n_stack=(stack_t*)malloc(sizeof(stack_t));
n_stack->top_stack=NULL;
return (*n_stack);
}
// Returns 1 if the stack is empty, 0 otherwise
int Empty(stack_t q)
{
if(q.top_stack==NULL)
return 1;
else
return 0;
}
// Returns 1 if the stack is full, 0 otherwise
int Full(stack_t q)
{
return 0;
}
// Pushes the element e in the stack. Returns 1 if it could Push.
int Push(int e, stack_t *q)
{
s_Node *nn;
nn= (s_Node*)malloc(sizeof(s_Node));
if(Full(*q))
{
printf("\n\t Stack is Full !! \n\n");
return 0; // return 0 if enstack NOT successful
}
else
{
nn->element=e;
nn->next=q->top_stack;
q->top_stack=nn;
return 1;
}
}
// Pops an element, placing it in e. Returns 1 if it could Pop.
int Pop(int *e, stack_t *q)
{
s_Node *temp;
if(Empty(*q)) // Check if the stack is empty
{
return 0; // popping Failed
}
else
{
temp=q->top_stack; // store the top in a temp ptr Node to free it after
*e=q->top_stack->element; // Store the popped element in e
q->top_stack=q->top_stack->next; // Point the top to the next element
free(temp); // Free the popped Node
return 1;
}
}
void Printstack(const stack_t q)
{
if(Empty(q))
printf("\n\tStack is empty!!\n");
else{
s_Node *walker;
walker = q.top_stack;
printf("\n\t This is the content of the stack:\n");
while(walker!=NULL)
{
printf("\t%d ",walker->element);
walker=walker->next;
}
printf("\n");
}
}
int Peek (stack_t s)
{ printf ("%d\n",s.top_stack->element);
return s.top_stack->element; // Returning the top element of the stack
}
提前谢谢。
答案 0 :(得分：1)
您在此处引用NULL：
int Peek (stack_t s)
{ printf ("%d\n",s.top_stack->element);
在此序列中：
else
{
while ( newint > Peek (stack1) )
{ //Repeat poping from stack1 and pushing into stack2
// until it the integer read from the file is bigger than the top element of stack1
printf ("gOT into THE WHILE LOOP\n");
Pop (&val1,&stack1);
Push (val1, &stack2);
Printstack (stack2);
}
由于您的输入列表：
2 1 3
3比堆叠中的所有内容都大，因此在查找大于3的元素时，pop关闭所有内容，使stack1.top_stack为NULL。你的支票应该是：
while (!Empty(stack1) && (newint > Peek (stack1)))
答案 1 :(得分：0)
更改
while ( newint > Peek (stack1) )
到
while ( !Empty(stack1) && newint > Peek (stack1) )
由于你的peek函数不处理Empty stacks，你必须明确检查它。