add Doubly Linked List

Author: Code-Recursion

Linked Lists/Doubly Linked list/delete_dll.c

@@ -0,0 +1,122 @@
+#include <stdio.h>
+#include <stdlib.h>
+struct Node
+{
+    struct Node *prev;
+    int data;
+    struct Node *next;
+} *first = NULL;
+
+void Create(int A[], int n)
+{
+    struct Node *t, *last;
+    int i;
+    first = (struct Node *)malloc(sizeof(struct Node));
+    first->data = A[0];
+    first->prev = first->next = NULL;
+    last = first;
+    for (int i = 1; i < n; i++)
+    {
+        t = (struct Node *)malloc(sizeof(struct Node));
+        t->data = A[i];
+        t->next = last->next;
+        t->prev = last;
+        last->next = t;
+        last = t;
+    }
+}
+
+void Display(struct Node *p)
+{
+    while (p)
+    {
+        printf("%d ", p->data);
+        p = p->next;
+    }
+    printf("\n");
+}
+
+int Length(struct Node *p)
+{
+    int len = 0;
+    while (p)
+    {
+        len++;
+        p = p->next;
+    }
+    return len;
+}
+
+void Insert(struct Node *p, int index, int x)
+{
+    struct Node *t;
+    int i;
+
+    if (index < 0 || index > Length(p))
+        return;
+    if (index == 0)
+    {
+        t = (struct Node *)malloc(sizeof(struct Node));
+        t->data = x;
+        t->prev = NULL;
+        t->next = first;
+        first->prev = t;
+        first = t;
+    }
+    else
+    {
+        for (int i = 0; i < index - 1; i++)
+            p = p->next;
+
+        t = (struct Node *)malloc(sizeof(struct Node));
+        t->data = x;
+        t->next = p->next;
+        t->prev = p;
+        if (p->next) // if next node is present
+            p->next->prev = t;
+        p->next = t;
+    }
+}
+
+int Delete(struct Node *p, int index)
+{
+    struct Node *q;
+    int x = -1, i;
+    if (index < 1 || index > Length(p))
+        return -1;
+    if (index == 1)
+    {
+        first = first->next;
+        if (first)
+            first->prev = NULL;
+        x = p->data;
+        free(p);
+    }
+    else
+    {
+        for (i = 0; i < index - 1; i++)
+            p = p->next;
+        p->prev->next = p->next;
+        if (p->next)
+            p->next->prev = p->prev;
+        x = p->data;
+        free(p);
+    }
+    return x;
+}
+int main()
+{
+    int A[] = {10, 20, 30, 40, 50};
+    Create(A, 5);
+    printf("Deleted : %d\n", Delete(first, 4));
+    Display(first);
+
+    return 0;
+}
+
+// Deleted : 40
+// 10 20 30 50
+
+// Time
+// Min : O(1)
+// Max : O(n)

Linked Lists/Doubly Linked list/display_dll.c

@@ -0,0 +1,58 @@
+#include <stdio.h>
+#include <stdlib.h>
+struct Node
+{
+    struct Node *prev;
+    int data;
+    struct Node *next;
+} *first = NULL;
+
+void Create(int A[], int n)
+{
+    struct Node *t, *last;
+    int i;
+    first = (struct Node *)malloc(sizeof(struct Node));
+    first->data = A[0];
+    first->prev = first->next = NULL;
+    last = first;
+    for (int i = 1; i < n; i++)
+    {
+        t = (struct Node *)malloc(sizeof(struct Node));
+        t->data = A[i];
+        t->next = last->next;
+        t->prev = last;
+        last->next = t;
+        last = t;
+    }
+}
+
+void Display(struct Node *p)
+{
+    while (p)
+    {
+        printf("%d ", p->data);
+        p = p->next;
+    }
+    printf("\n");
+}
+
+int Length(struct Node *p)
+{
+    int len = 0;
+    while (p)
+    {
+        len++;
+        p = p->next;
+    }
+    return len;
+}
+
+int main()
+{
+    int A[] = {10, 20, 30, 40, 50};
+    Create(A, 5);
+    printf("\nLength : %d\n", Length(first));
+    Display(first);
+
+    return 0;
+}

Linked Lists/Doubly Linked list/insert_dll.c

@@ -0,0 +1,96 @@
+#include <stdio.h>
+#include <stdlib.h>
+struct Node
+{
+    struct Node *prev;
+    int data;
+    struct Node *next;
+} *first = NULL;
+
+void Create(int A[], int n)
+{
+    struct Node *t, *last;
+    int i;
+    first = (struct Node *)malloc(sizeof(struct Node));
+    first->data = A[0];
+    first->prev = first->next = NULL;
+    last = first;
+    for (int i = 1; i < n; i++)
+    {
+        t = (struct Node *)malloc(sizeof(struct Node));
+        t->data = A[i];
+        t->next = last->next;
+        t->prev = last;
+        last->next = t;
+        last = t;
+    }
+}
+
+void Display(struct Node *p)
+{
+    while (p)
+    {
+        printf("%d ", p->data);
+        p = p->next;
+    }
+    printf("\n");
+}
+
+int Length(struct Node *p)
+{
+    int len = 0;
+    while (p)
+    {
+        len++;
+        p = p->next;
+    }
+    return len;
+}
+
+void Insert(struct Node *p, int index, int x)
+{
+    struct Node *t;
+    int i;
+
+    if (index < 0 || index > Length(p))
+        return;
+    if (index == 0)
+    {
+        t = (struct Node *)malloc(sizeof(struct Node));
+        t->data = x;
+        t->prev = NULL;
+        t->next = first;
+        first->prev = t;
+        first = t;
+    }
+    else
+    {
+        for (int i = 0; i < index - 1; i++)
+            p = p->next;
+
+        t = (struct Node *)malloc(sizeof(struct Node));
+        t->data = x;
+        t->next = p->next;
+        t->prev = p;
+        if (p->next) // if next node is present
+            p->next->prev = t;
+        p->next = t;
+    }
+}
+
+int main()
+{
+    int A[] = {10, 20, 30, 40, 50};
+    Create(A, 5);
+    Insert(first, 0, 25);
+    Display(first);
+
+    return 0;
+}
+
+// Output :
+// 25 10 20 30 40 50
+
+// Time:
+// inserting at first = constant time
+// insert at an given index = O(n)