Question

How to add element after an element in a linked list in C

Answer 1

#include <stdio.h>
#include <stdlib.h>
 
typedef struct Node {
    int x;
    struct Node *next;
} Node;
  
void add_after(Node *node, int value) {
    Node* new_node = malloc(sizeof(Node));
    
    if (new_node == NULL) {
        puts("malloc error");
        exit(1);
    }
    
    new_node->x = value;
    new_node->next = node->next;
    node->next = new_node;
}
  
void add_node(Node **root, int value) {
    Node *new_node = malloc(sizeof(Node));
      
    if (new_node == NULL) {
        puts("malloc error");
        exit(1);
    }
      
    new_node->next = NULL;
    new_node->x = value;
      
    if (*root == NULL) {
        *root = new_node;
        return;
    }
      
    Node* current = *root;
    while (current->next != NULL) {
        current = current->next;
    }
    current->next = new_node;
}
  
void free_LinkedList(Node *root) {
    Node *next;
    while (root != NULL)  {  
        next = root->next;  
        free(root);  
        root = next;  
    }  
}
  
int main() {
    Node *root = NULL;
      
    add_node(&root, 7);
    add_node(&root, 3);
    add_node(&root, 78);
    add_node(&root, 200);
      
    for (Node *current = root; current != NULL; current = current->next) {
        printf("%d\n", current->x);
    }
     
    add_after(root, 1000);
     
    puts("\n");
    for (Node *current = root; current != NULL; current = current->next) {
        printf("%d\n", current->x);
    }
    
    add_after(root->next, 9);
     
    puts("\n");
    for (Node *current = root; current != NULL; current = current->next) {
        printf("%d\n", current->x);
    }
      
    free_LinkedList(root);
  
    return 0;
}
  
  
  
/*
run:
  
7
3
78
200


7
1000
3
78
200


7
1000
9
3
78
200
 
*/

 

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