c - 在 C 中使用两个堆栈实现一个队列

Question

为什么我的代码在运行时会崩溃。它说在 Push() 函数中传递不兼容的指针类型。如何解决这个问题？

这是我在 C 中实现的代码。这是我如何尝试解决问题的快速总结。

• 首先我为 Stack 创建了一个结构
• 为堆栈编写 Push 和 Pop 函数
• 为队列编写了一个结构

• EnQueue 的第一个堆栈和 DeQueue 操作的第二个堆栈。

  #include <stdio.h>
  #include <stdlib.h>
  #include <limits.h>
  
  struct Stack {
      int data;
      struct Stack *next;
  };
  
  
  struct Stack *CreateStack () {
      return NULL;
  }
  
  int isEmptyStack(struct Stack *top) {
      return (top == NULL);
  }
  
  void Push(struct Stack **top, int data) {
      struct Stack *newNode = (struct Stack*) malloc(sizeof(struct Stack));
      if(!newNode)
          return;
      newNode->data = data;
      newNode->next = *top;
      *top = newNode;
  }
  
  int Pop(struct Stack **top) {
      struct Stack *temp;
      int data;
  
      if(isEmptyStack(*top)) {
          printf("Empty Stack.\n");
          return INT_MIN;
      }
  
      temp = *top;
      data = (*top)->data;
      *top = (*top)->next;
      free(temp);
      return data;
  }
  
  struct Queue {
      struct Stack *S1;
      struct Stack *S2;
  };
  
  struct Queue *CreateQueue() {
      return NULL;
  }
  
  void EnQueue(struct Queue *Q, int data) {
      Push(Q->S1, data);
  }
  
  int DeQueue(struct Queue *Q) {
      if(!isEmptyStack(Q->S2)) {
          return Pop(Q->S2);
      }
      else {
          while(!isEmptyStack(Q->S1)) {
              Push(Q->S2, Pop(Q->S1));
          }
          return Pop(Q->S2);
      }
  }
  
  int main() {
      struct Queue *Q = CreateQueue();
      Q->S1 = Q->S2 = NULL;
      EnQueue(Q, 1);
      EnQueue(Q, 2);
      EnQueue(Q, 3);
  
      printf("%d ", DeQueue(Q));
      printf("%d ", DeQueue(Q));
      printf("%d ", DeQueue(Q));
  
      return 0;
  }
  

Answer 1

三个问题:

a) 调用 Push - 错误的参数类型:struct Stack **top 应该不是 struct Stack *top

b) 调用 Pop - 错误的参数类型:struct Stack **top 应该不是 struct Stack *top

c) 队列 *CreateQueue - 未分配内存

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

struct Stack {
    int data;
    struct Stack *next;
};


struct Stack *CreateStack () {
    return NULL;
}

int isEmptyStack(struct Stack *top) {
    return (top == NULL);
}

void Push(struct Stack **top, int data) {
    struct Stack *newNode = (struct Stack*) malloc(sizeof(struct Stack));
    if(!newNode)
        return;
    newNode->data = data;
    newNode->next = *top;
    *top = newNode;
}

int Pop(struct Stack **top) {
    struct Stack *temp;
    int data;

    if(isEmptyStack(*top)) {
        printf("Empty Stack.\n");
        return INT_MIN;
    }

    temp = *top;
    data = (*top)->data;
    *top = (*top)->next;
    free(temp);
    return data;
}

struct Queue {
    struct Stack *S1;
    struct Stack *S2;
};

struct Queue *CreateQueue() {

    struct  Queue  *newNode = (struct Queue *) malloc(sizeof(struct  Queue ));

    return newNode;
}

void EnQueue(struct Queue *Q, int data) {
    Push(&Q->S1, data);
}

int DeQueue(struct Queue *Q) {
    if(!isEmptyStack(Q->S2)) {
        return Pop(&Q->S2);
    }
    else {
        while(!isEmptyStack(Q->S1)) {
            Push(&Q->S2, Pop(&Q->S1));
        }
        return Pop(&Q->S2);
    }
}

int main() {
    struct Queue *Q = CreateQueue();
    Q->S1 = Q->S2 = NULL;
    EnQueue(Q, 1);
    EnQueue(Q, 2);
    EnQueue(Q, 3);

    printf("%d ", DeQueue(Q));
    printf("%d ", DeQueue(Q));
    printf("%d ", DeQueue(Q));

    return 0;
}

输出:

1 2 3