Language: C

#include<stdio.h>
#include<string.h>
#include<stdlib.h>
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void init(); //?????????????????????
void insert(int ); //??????????????????
struct Node* listSearch(int );
void deleteNode(struct Node *);
void deleteFirst();
void deleteLast();
void deleteKey(int );
void print();
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struct Node{
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????int key;
????struct Node *prev;
????struct Node *next;
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};
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struct Node *NIL =NULL;
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int main(){
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  ????int sumcommand,i,key;
 ????char command[10];
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     ????init();
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	 ????scanf("%d",&sumcommand);
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	     ????for(i = 0; i < sumcommand; i++){
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    ????????scanf("%s",command);
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		   ????????if((strcmp("insert",command)) == 0){
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      ????????????scanf("%d",&key);
      ????????????insert(key);
??????????
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	      ????????}
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			 ????????else if((strcmp("delete",command)) == 0){
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      ????????????scanf("%d",&key);
      ????????????deleteKey(key);
      ????????}
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			 ????????else if((strcmp("deleteFirst",command))==0){
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      ????????????deleteFirst();
      ????????}
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			 ????????else if((strcmp("deleteLast",command))== 0){
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      ??????????????deleteLast();
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	????????}
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			 ????}
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		 ????print();
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		     ????return 0;
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			 }
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void init(){
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  ????NIL = (struct Node *)malloc(sizeof(struct Node));
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    ????NIL->next?? = NIL;
 ????NIL->prev = NIL;
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     }
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void insert(int key){
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  ????struct Node *x = (struct Node*)malloc(sizeof(struct Node));
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    ????x -> key = key;
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	????x->next = NIL->next;
 ????NIL->next->prev = x;
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     ????NIL->next = x;
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	 ????x->prev = NIL;
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	     }
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struct Node* listSearch(int key){
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 ????struct Node *y = NIL->next;
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    ????while(y != NIL && y->key != key){
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 ????????y = y->next;
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	  ????}
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	????return y;
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	    }
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void deleteNode(struct Node *x){
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  ????if(x == NIL){
??????????
 ????????return ;
??????
      ????}
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    ????x->prev->next = x->next;
 ????x->next->prev = x->prev;
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     ??????free(x);
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??????
	  }
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void deleteFirst(){
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  ????deleteNode(NIL->next);
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    }
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void deleteLast(){
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  ????deleteNode(NIL->prev);
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    }
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void deleteKey(int key){
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  ????deleteNode(listSearch(key));
}
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void print(){
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 ????struct Node *z = NIL->next;
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    ????int x;
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	????while(1){
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    ????????if(z == NIL){
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 ????????????break;
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		????????}
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	      ????????if(x++ > 0){
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      ????????????printf(" ");
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		      ????????}
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		    ????????printf("%d", z->key);
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			  ????????z = z->next;
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				????}
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	    ????printf("\n");
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		}

Compiler output:
main.c:4:1: error: expected identifier or '(' before '?' token
    4 | ??
      | ^
main.c:13:1: error: expected identifier or '(' before '?' token
   13 | ??
      | ^
main.c:21:1: error: expected identifier or '(' before '?' token
   21 | ??
      | ^
main.c:23:1: error: expected identifier or '(' before '?' token
   23 | ??
      | ^
main.c:69:1: error: expected identifier or '(' before '?' token
   69 | ??
      | ^
main.c:78:1: error: expected identifier or '(' before '?' token
   78 | ??
      | ^
main.c:94:1: error: expected identifier or '(' before '?' token
   94 | ??
      | ^
main.c:109:1: error: expected identifier or '(' before '?' token
  109 | ??
      | ^
main.c:125:1: error: expected identifier or '(' before '?' token
  125 | ??
      | ^
main.c:131:1: error: expected identifier or '(' before '?' token
  131 | ??
      | ^
main.c:137:1: error: expected identifier or '(' before '?' token
  137 | ??
      | ^
main.c:142:1: error: expected identifier or '(' before '?' token
  142 | ??
      | ^