Double Linked List

1:  /*Doubly linked list*/  
2:  #include<stdio.h>  
3:  #include<conio.h>  
4:  #include<alloc.h>  
5:  struct node  
6:  {  
7:    int data;  
8:    struct node*left;  
9:    struct node*right;  
10:  }*n;  
11:  struct node*head,*ne,*last,*p,*t;  
12:  char opt;  
13:  int no,ch;  
14:  void create(struct node*n);  
15:  void insert(struct node*n);  
16:  void infir(struct node*n);  
17:  void inlast(struct node*n);  
18:  void inmid(struct node*n);  
19:  void delfir(struct node*n);  
20:  void del(struct node*n);  
21:  void delast(struct node*n);  
22:  void delmid(struct node*n);  
23:  void display(struct node*n);  
24:  void main()  
25:  {  
26:    clrscr();  
27:    printf("\n\t\t\tDOUBLY LINKED LIST\t\t\t\n");  
28:    while(1)  
29:    {  
30:        printf("\n1.CREATION\n2.INSERTION\n3.DELETION\n4.DISPLAY\n5.EXIT\n");  
31:        printf("\nEnter ur choice");  
32:        scanf("%d",&ch);  
33:        switch(ch)  
34:        {  
35:          case 1:  
36:                 create(n);  
37:                 break;  
38:          case 2:  
39:                 insert(n);  
40:                 break;  
41:          case 3:  
42:                 del(n);  
43:                 break;  
44:          case 4:  
45:                 display(n);  
46:                 break;  
47:          case 5:  
48:                 exit(1);  
49:                 break;  
50:          default:  
51:                 printf("\nEnter a valid case\n");  
52:                 break;  
53:        }  
54:    }  
55:  }  
56:  void create(struct node*n)  
57:  {  
58:    ne=(struct node*)malloc(sizeof(struct node));  
59:    printf("\nEnter the data:");  
60:    scanf("%d",&(ne->data));  
61:    head=ne;  
62:    ne->left=NULL;  
63:    ne->right=NULL;  
64:    printf("\nDo u wish to create another?:(y/n):");  
65:    scanf("%c",&opt);  
66:    //fflush(stdin);  
67:    opt=getchar();  
68:    while(opt=='y')  
69:    {  
70:        if(head->right==NULL)  
71:        {  
72:          ne=(struct node*)malloc(sizeof(struct node));  
73:          printf("\nEnter the data:");  
74:          scanf("%d",&(ne->data));  
75:          ne->left=head;  
76:          ne->right=NULL;  
77:          head->right=ne;  
78:        }  
79:        else  
80:        {  
81:          p=head;  
82:          while(p->right!=NULL)  
83:          {  
84:              p=p->right;  
85:          }  
86:          ne=(struct node*)malloc(sizeof(struct node));  
87:          printf("\nEnter the data:");  
88:          scanf("%d",&(ne->data));  
89:          ne->right=NULL;  
90:          ne->left=p;  
91:          p->right=ne;  
92:        }  
93:        printf("\nDo u wish to create another(y/n)?:");  
94:        scanf("%c",&opt);  
95:        opt=getchar();  
96:    }  
97:  }  
98:  void insert(struct node*n)  
99:  {  
100:    printf("\nDo u want to insert?(y/n):");  
101:    scanf("%c",&opt);  
102:    opt=getchar();  
103:    while(opt=='y')  
104:    {  
105:        printf("\n\t\tINSERTION\t\t\n");  
106:        printf("\n1.FRONT\n2.MIDDLE\n3.END\n");  
107:        printf("\nEnter ur choice:");  
108:        scanf("%d",&ch);  
109:        switch(ch)  
110:        {  
111:          case 1:  
112:                 infir(n);  
113:                 break;  
114:          case 2:  
115:                 inmid(n);  
116:                 break;  
117:          case 3:  
118:                 inlast(n);  
119:                 break;  
120:        }  
121:    }  
122:  }  
123:  void infir(struct node*n)  
124:  {  
125:    printf("\nDo u wish to insert?(y/n)?:");  
126:    scanf("%c",&opt);  
127:    opt=getchar();  
128:    while(opt=='y')  
129:    {  
130:        p=head;  
131:        ne=(struct node*)malloc(sizeof(struct node));  
132:        printf("\nEnter the data:");  
133:        scanf("%d",&(ne->data));  
134:        ne->right=p;  
135:        ne->left=NULL;  
136:        printf("\nThe data %d of the node allocated has been inserted at the front\n",ne->data);  
137:        printf("\nDo u wish to insert(y/n)?:");  
138:        scanf("%c",&opt);  
139:        opt=getchar();  
140:    }  
141:  }  
142:  void inlast(struct node*n)  
143:  {  
144:    printf("\nDo u wish to insert(y/n)?:");  
145:    scanf("%c",&opt);  
146:    opt=getchar();  
147:    while(opt=='y')  
148:    {  
149:        ne=(struct node*)malloc(sizeof(struct node));  
150:        printf("\nEnter the data:");  
151:        scanf("%d",&(ne->data));  
152:        p=head;  
153:        while(p->right!=NULL)  
154:        {  
155:          p=p->right;  
156:        }  
157:        p->right=ne;  
158:        ne->left=p;  
159:        ne->right=NULL;  
160:        printf("\nThe data %d of the node allocated has been inserted at the end\n",ne->data);  
161:        printf("\nDo u wish to insert(y/n)?:");  
162:        scanf("%c",&opt);  
163:        opt=getchar();  
164:    }  
165:  }  
166:  void inmid(struct node*n)  
167:  {  
168:    printf("\nDo u wish to insert(y/n)?:");  
169:    scanf("%c",&opt);  
170:    opt=getchar();  
171:    while(opt=='y')  
172:    {  
173:        p=head;  
174:        printf("\nEnter the data of the node after which u want to insert:");  
175:        scanf("%d",&no);  
176:        while(p->data!=no)  
177:        {  
178:          p=p->right;  
179:        }  
180:        ne=(struct node*)malloc(sizeof(struct node));  
181:        printf("\nEnter the data:");  
182:        scanf("%d",&(ne->data));  
183:        ne->right=p->right;  
184:        ne->left=p;  
185:        p->right->left=ne;  
186:        p->right=ne;  
187:        printf("\nThe data %d of the allocated node has been inserted at the middle\n");  
188:        printf("\nDo u wish to insert(y/n)?:");  
189:        scanf("%c",&opt);  
190:        opt=getchar();  
191:    }  
192:  }  
193:  void delfir(struct node*n)  
194:  {  
195:    t=head;  
196:    p=head;  
197:    head=head->right;  
198:    head->left=NULL;  
199:    free(t);  
200:    printf("\nThe deleted node at the front holds the data %d\n",t->data);  
201:    free(t);  
202:  }  
203:  void delast(struct node*n)  
204:  {  
205:    p=head;  
206:    while(p->right->right!=NULL)  
207:    {  
208:        p=p->right;  
209:    }  
210:    t=p;  
211:    p->right=NULL;  
212:    printf("\nThe deleted node at the end holds the data %d\n",t->data);  
213:    free(t);  
214:    return;  
215:  }  
216:  void delmid(struct node*n)  
217:  {  
218:    printf("\nEnter the data of the node after which you want to delete?:");  
219:    scanf("%d",&(no));  
220:    p=head;  
221:    while(p->right->data!=no)  
222:    {  
223:        p=p->right;  
224:    }  
225:    t=p;  
226:    p->left->right=p->right;  
227:    p->right->left=p->left;  
228:    printf("\nThe deleted node is at mid position holding the data %d\n",t->data);  
229:    free(t);  
230:    return;  
231:  }  
232:  void del(struct node*n)  
233:  {  
234:    printf("\n\t\tDELETION\t\t\n");  
235:    if(head==NULL)  
236:    {  
237:        printf("\nNO Nodes\n");  
238:        return;  
239:    }  
240:    else  
241:    {  
242:        printf("\n1.FRONT\n2.MIDDLE\n3.END\n");  
243:        printf("\nEnter the choice:");  
244:        scanf("%d",&ch);  
245:        switch(ch)  
246:        {  
247:          case 1:  
248:                 delfir(n);  
249:                 break;  
250:          case 2:  
251:                 delmid(n);  
252:                 break;  
253:          case 3:  
254:                 delast(n);  
255:                 break;  
256:        }  
257:    }  
258:  }  
259:  void display(struct node *n)  
260:  {  
261:    if(head==NULL)  
262:    {  
263:        printf("\nNO Nodes\n");  
264:        return;  
265:    }  
266:    printf("\nThe items in the list are\n");  
267:    t=head;  
268:    do  
269:    {  
270:        printf("|%d|--->",t->data);  
271:        t=t->right;  
272:    }  
273:    while(t->right!=NULL);  
274:    printf("|%d|--->",t->data);  
275:    printf("|NULL|");  
276:  }