双链表分段错误后向打印

Question

我试图在特定位置删除节点，但我一直得到分段错误11.

我正在从文件中读取位置和值。

下面是我的代码:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
typedef struct node {
  float val;
  struct node *prev;
  struct node *next;
}node_t;
void printForward(node_t *head) {
  node_t *current = head;
  while (current != NULL) {
    printf("%.2fn", current->val);
    current = current->next;
  }
}
void printBackward(node_t *head) {
  node_t *current = head;
  while (current->next != NULL) {
    current = current->next;
  }
  while (current != NULL) {
    printf("%.2fn", current->val);
    current = current->prev;
  }
}

void deleteAtPos(node_t **head, int pos) {
  int i;
  node_t *current = *head;
  node_t *temp = NULL;
  if (pos == 0) {
    temp = (*head)->next;
    free(*head);
    (*head) = temp;
    (*head)->prev = NULL;
    return;
  }
    for (i = 0; i < (pos - 1); i++) {
      if (current->next != NULL) {
        current = current->next;
      }
    }
      temp = current->next;
      current->next = temp->next;
      free(temp);
}

// Fix insert at position
void insertAtPos(node_t **head, int pos, float val) {
  int i;
  node_t *newNode = malloc(sizeof(node_t));
  node_t *current = *head;
  newNode->val = val;
  if (pos == 0) {
    newNode->next = (*head);
    newNode->prev = NULL;
    (*head)->prev = newNode;
    (*head) = newNode;
    return;
  }
  for (i = 0; i < pos; i++) {
    if (current->next != NULL) {
      current = current->next;
    }
    else {
      printf("Node does not existn");
      break;
    }
  }
  current->prev->next = newNode;
  newNode->prev = current->prev;
  newNode->next = current;
  current->prev = newNode;
}
void addEnd(node_t **head, float val) {
  node_t *current = *head;
  node_t *newNode = malloc(sizeof(node_t));
  newNode->next = NULL;
  newNode->val = val;
  if (*head == NULL) {
    *head = newNode;
    newNode->prev = NULL;
    return;
  }
  while (current->next != NULL) {
    current = current->next;
  }
  current->next = newNode;
  newNode->prev = current;
}
int main(int argc, char *argv[]) {
  if (argc != 2) {
    printf("Error");
  }
  node_t *head = NULL;
  FILE *fp;
  int i = 0, x;
  float valLine1, valLine2, valLine3;
  char buffer[200], *token, *del = ",";
  float posVals[200], delPos[200];
  fp = fopen(argv[1], "r");
  fgets(buffer, sizeof(buffer), fp);
    token = strtok(buffer, del);
    while (token != NULL) {
      valLine1 = atof(token);
      addEnd(&head, valLine1);
      token = strtok(NULL, del);
    }
    printForward(head);
    printf("n");

    del = ":,";
    fgets(buffer, sizeof(buffer), fp);
    token = strtok(buffer, del);
    while (token != NULL) {
      valLine2 = atof(token);
      posVals[i] = valLine2;
      token = strtok(NULL, del);
      i++;
    }
    for (x = 0; x < i; x += 2) {
      insertAtPos(&head, posVals[x + 1], posVals[x]);
    }
    printForward(head);
    fgets(buffer, sizeof(buffer), fp);
    i = 0;
    token = strtok(buffer, del);
    while (token != NULL) {
      valLine3 = atof(token);
      delPos[i] = valLine3;
      token = strtok(NULL, del);
      i++;
    }
    printf("n");

    for (x = 0; x < i; x++) {
      deleteAtPos(&head, delPos[x]);
    }

    printForward(head);
    printf("n");
    printBackward(head);
    fclose(fp);

}

问题是我的deleteAtPos函数，但我不知道为什么。

输出如下:

24.00
0.04
17.00
-200.10
34.60
0.00
Segmentation fault: 11

文件的内容如下:

17,32.5,12,0,34.6,-200.1,17,0.04,24
1:2,4.1:5,-12:4
3,5,0

请帮忙!

谢谢

Answer 1

我已经修改了你的deleteAtPos()函数，现在你可以在任何位置删除，你的backward()函数将打印正确的值。

void deleteAtPos(node_t **head, int pos) {
  int i;
  node_t *current = *head;
  node_t *temp = NULL;    
  if (pos == 0) {
    temp = (*head)->next;
    free(*head);
    (*head) = temp;
    (*head)->prev = NULL;
    return;
  }
    for (i = 0; i < (pos - 1); i++) {
      if (current->next != NULL) {
        current = current->next;
      }
    }

    temp = current;
    if(current->next==NULL)
    {
        current->prev->next = current->next;
    }
    else
    {
        current->prev->next = current->next;
        current->next->prev = current->prev;
    }
    free(temp);
}

Answer 2

你是说问题出在deleteAtPos。但是你的代码离SSCCE还很远，所以我不想为你隔离问题——你应该这样做，大多数时候，在隔离的过程中，你会找到答案。如果没有，你可以把问题贴在这里。

因此，我将列出我能看到的deleteAtPos错误的事情，也许如果你解决了所有这些问题，问题就会消失。

1. 您没有处理*head为NULL的情况，列表有0个元素。

2. 您没有检查pos >= 0

3. 您没有正确处理列表中有一个元素的情况。另一段错误。

4. 您没有正确处理pos是列表末尾的情况。另一段错误。