delete function in a singly linked list in c

1// A complete working C program
2// to demonstrate deletion in
3// singly linked list
4#include <stdio.h>
5#include <stdlib.h>
6 
7// A linked list node
8struct Node {
9    int data;
10    struct Node* next;
11};
12 
13/* Given a reference (pointer to pointer) to the head of a
14   list and an int, inserts a new node on the front of the
15   list. */
16void push(struct Node** head_ref, int new_data)
17{
18    struct Node* new_node
19        = (struct Node*)malloc(sizeof(struct Node));
20    new_node->data = new_data;
21    new_node->next = (*head_ref);
22    (*head_ref) = new_node;
23}
24 
25/* Given a reference (pointer to pointer) to the head of a
26   list and a key, deletes the first occurrence of key in
27   linked list */
28void deleteNode(struct Node** head_ref, int key)
29{
30    // Store head node
31    struct Node *temp = *head_ref, *prev;
32 
33    // If head node itself holds the key to be deleted
34    if (temp != NULL && temp->data == key) {
35        *head_ref = temp->next; // Changed head
36        free(temp); // free old head
37        return;
38    }
39 
40    // Search for the key to be deleted, keep track of the
41    // previous node as we need to change 'prev->next'
42    while (temp != NULL && temp->data != key) {
43        prev = temp;
44        temp = temp->next;
45    }
46 
47    // If key was not present in linked list
48    if (temp == NULL)
49        return;
50 
51    // Unlink the node from linked list
52    prev->next = temp->next;
53 
54    free(temp); // Free memory
55}
56 
57// This function prints contents of linked list starting
58// from the given node
59void printList(struct Node* node)
60{
61    while (node != NULL) {
62        printf(" %d ", node->data);
63        node = node->next;
64    }
65}
66 
67// Driver code
68int main()
69{
70    /* Start with the empty list */
71    struct Node* head = NULL;
72 
73    push(&head, 7);
74    push(&head, 1);
75    push(&head, 3);
76    push(&head, 2);
77 
78    puts("Created Linked List: ");
79    printList(head);
80    deleteNode(&head, 1);
81    puts("\nLinked List after Deletion of 1: ");
82    printList(head);
83    return 0;
84}

1#include<conio.h>
2#include<stdio.h>
3
4struct node
5{
6    int i;
7    struct node *next;
8};
9
10void main()
11{
12
13    struct node *first;
14    struct node *last;
15
16    struct node *temp;
17    int ch,user,add,cnt=0,t=0;
18    struct node *p;
19
20    clrscr();
21
22    printf("\n\t 1.CREATION");
23    printf("\n\t 2.INSERT AT STARTING");
24    printf("\n\t 3.INSERT AT MIDDLE(USER'S CHOICE)");
25    printf("\n\t 4.INSERT AT END");
26    printf("\n\t 5.DELETE 1ST NODE");
27    printf("\n\t 6.DELETE LAST NODE");
28    printf("\n\t 7.DELETE MIDDLE NODE(USER'S CHOICE)");
29    printf("\n\t 8.DISPLAY");
30    printf("\n\t 10.EXIT");
31    scanf("%d",&user);
32
33    while(user!=10)
34    {
35      if(user==1)
36      {
37        printf("\n\t ENTER DATA  ::: ");
38        first=(struct node*)malloc(sizeof(struct node));
39        scanf("%d",&ch);
40
41        first->i=ch;
42        first->next=0;
43        p=first;
44        cnt=1;
45      }
46      if(user==2)
47      {
48            p=(struct node*)malloc(sizeof(struct node));
49            printf("\n\t ENTER DATA FOR 1ST NODE");
50            scanf("%d",&p->i);
51            p->next=first;
52            first=p;
53            cnt++;
54      }
55      if(user==4)
56      {
57            p=(struct node*)malloc(sizeof(struct node));
58            printf("\n\t ENTER DATA FOR LAST NODE");
59            scanf("%d",&p->i);
60            temp=first;
61            while(temp->next!=0)
62            {
63                temp=temp->next;
64            }
65            temp->next=p;
66            p->next=0;
67            cnt++;
68      }
69      if(user==3)
70      {
71            printf("\n\t ENTER ANY ADDRESS BETWEEN 1 and %d",cnt);
72            scanf("%d",&add);
73
74            t=1;
75            p=first;
76            while(t!=add)
77            {
78                p=p->next;
79                t++;
80            }
81            temp=(struct node*)malloc(sizeof(struct node));
82            printf("\n\t ENTER DATA FOR NODE");
83            scanf("%d",&temp->i);
84            temp->next=p->next;
85            p->next=temp;
86            cnt++;
87      }
88      if(user==5)
89      {
90            p=first;
91            first=p->next;
92            free(p);
93      }
94      if(user==6)
95      {
96        p=first;
97        while(p->next->next!=0)
98        {
99            p=p->next;
100        }
101        p->next=0;
102        free(p->next->next);
103      }
104      if(user==8)
105      {
106        p=first;
107        while(p!=0)
108        {
109            printf("\n\t %d",p->i);
110            p=p->next;
111        }
112      }
113      if(user==7)
114      {
115            printf("\n\t ENTER ANY ADDRESS BETWEEN 1 and %d",cnt);
116            scanf("%d",&add);
117
118            t=1;
119            p=first;
120            while(t<add-1)
121            {
122                p=p->next;
123                t++;
124            }
125            temp=p->next;
126            p->next=temp->next;
127            free(temp);
128            cnt--;
129
130      }
131      printf("\n\t 1.CREATION");
132      printf("\n\t 2.INSERT AT STARTING");
133      printf("\n\t 3.INSERT AT MIDDLE(USER'S CHOICE)");
134      printf("\n\t 4.INSERT AT END");
135      printf("\n\t 5.DELETE 1ST NODE");
136      printf("\n\t 6.DELETE LAST NODE");
137      printf("\n\t 7.DELETE MIDDLE NODE(USER'S CHOICE)");
138      printf("\n\t 8.DISPLAY");
139      printf("\n\t 10.EXIT");
140      scanf("%d",&user);
141       }
142       getch();
143}

1typedef struct node{
2    int value; //this is the value the node stores
3    struct node *next; //this is the node the current node points to. this is how the nodes link
4}node;
5
6node *rmvNode(node *head, int index){
7    node *tmp = head;
8    node *rmv;
9    int count = 0;
10
11    //base case for if the user enters a value greater then or equal to the length of the head
12    //base case for if the user enters a value with a list of length 1. because in this library a list MUST contain one value minimum
13    if(index >= len(head) || len(head) == 1){
14        return NULL;
15    }
16  
17    //if you want to remove the first value
18    if(index == 0){
19        rmv = head; //stores the head at this given moment in time
20        head = tmp->next; //this jumps the position of the head making sure that the beginning is no longer part of the head
21        free(rmv); //this frees the memory given to the initial head
22        return head;
23    }
24
25    //if you want to remove index position 1
26    if(index == 1){
27        rmv = head->next;
28        head->next = tmp->next->next;
29        free(rmv);
30        return head;
31    }
32
33    //if you want to remove the last value
34    if(index == -1){
35        
36        while(count < len(head)-2){ //we do -2 because we want to access the node before the last one
37            tmp = tmp->next;
38            count += 1;
39        }
40        rmv = tmp->next;
41        tmp->next = NULL;
42        free(rmv);
43        return head;
44    }
45
46    //remove anything else
47    while(count < index-1){
48        tmp = tmp->next;
49        count += 1;
50    }
51    rmv = tmp->next;
52    tmp->next = tmp->next->next;
53    free(rmv);
54    return head;
55
56}