释放一系列链接列表

Question

因此，我无法释放已分配给我的链接列表数组的内存。

这里是我的typedef struct：

typedef struct Node { 
    int id; 
    int degree; 
    int distance; 
    int status; 
    struct Node *next; 
} Node; 

这里就是我创建阵列

Node *graph = malloc(sizeof(Node) * N); 
if (graph == NULL) { 
    printf("Fatal Error: Out of memory!\n"); 
    exit(1); 
} 
for (int i=0; i < N; i++) { 
    n = create_node(i); 
    graph[i] = *(n); 
} 
Node *graph2 = malloc(sizeof(Node) * N); 
if (graph2 == NULL) { 
    printf("Fatal Error: Out of memory!\n"); 
    exit(1); 
} 
for (int i=0; i < N; i++) { 
    n = create_node(i); 
    graph2[i] = *(n); 
} 

这里是create_node：

Node* create_node(int id) { 
    // Allocate memory for the structure 
    Node *n = malloc(sizeof (Node)); 
    if (n == NULL) { 
     printf("Fatal Error: Out of memory!\n"); 
     exit(1); 
    } 
    n->id = id; // set the value that identifies the node 
    n->distance = INT_MAX; //we don't know teh source yet, so distance is infinity 
    n->next = NULL; 
    n->status = 0; 
    return n; } 

这里是我尝试免费的代码阵列

for (int i=0; i < N; i++) { 
    free_node(&graph[i]);//<---here 
    graph = NULL; 
    free_node(&graph2[i]); 
    graph2 = NULL; 
} 

这是我free_node功能：

int free_node(Node *n) { 
    Node *tmp = malloc(sizeof(Node)); 
    while (n != NULL) {//<---here 
     tmp = n; 
     n = n.next; 
     free(tmp); 
     tmp = NULL; 
    } 
    return 0; 
} 

我得到的代码标记以上的线路分段错误的“< ---在这里”为在该行结尾的注释。它从我的free_node函数开始，它从释放graph[i]被调用。

Answer 1

• 您正在尝试通过发送struct的指针来释放一个struct有你的第一次迭代后分配NULL值这些指针，使他们danging指针。

检查以下修复程序：

for (int i=0; i < N; i++) { 
    free_node(graph + i); 
    free_node(graph2 + i); 
} 

Answer 2

链表（实际上2个阵列这里）的数组应该是一个指针数组的每个链接列表的第一个节点。您创建了Node的数组，然后丢弃了内存指针，因此您以后尝试释放内存失败。

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

#define N 10   // number of lists 

typedef struct Node { 
    int id; 
    int degree; 
    int distance; 
    int status; 
    struct Node *next; 
} Node; 

Node **graph, **graph2; 

Node* add_node(Node *root, int id) { 
    // Add a node to the list with begins at root, return new root 
    Node *n = malloc(sizeof (Node)); 
    if (n == NULL) { 
     printf("Fatal Error: Out of memory!\n"); 
     exit(1); 
    } 
    n->id = id; 
    n->degree = 0; 
    n->distance = INT_MAX; 
    n->status = 0; 
    n->next = root; 
    return n; 
} 

void free_list(Node *root) { 
    // free the list which starts with root 
    Node *tmp; 
    while (root) { 
     tmp = root->next;  
     free(root); 
     root = tmp; 
    } 
} 

int main(void) { 
    int i; 
    Node *tmp; 

    // create the arrays 
    graph = malloc(sizeof(Node*) * N); 
    if (graph == NULL) { 
     printf("Fatal Error: Out of memory!\n"); 
     exit(1); 
    } 
    graph2 = malloc(sizeof(Node*) * N); 
    if (graph2 == NULL) { 
     printf("Fatal Error: Out of memory!\n"); 
     exit(1); 
    } 
    for (i=0; i < N; i++) { 
     graph[i] = NULL; 
     graph2[i] = NULL; 
    } 

    // create one list 
    for (i=0; i < 12; i++) 
     graph[3] = add_node (graph[3], i); 

    // check the list 
    tmp = graph [3]; 
    while (tmp) { 
     printf ("%d ", tmp->id); 
     tmp = tmp->next; 
    } 

    // free the linked lists 
    for (i=0; i < N; i++) { 
     free_list(graph[i]); 
     graph[i] = NULL; // added later 
     free_list(graph2[i]); 
     graph2[i] = NULL; // added later 
    } 
    // free the arrays 
    free (graph); 
    free (graph2); 

    return 0; 
}