Hello Friends, i am having a hard time coding for 8 Puzzle using DFS (depth first search). my code uses linked list but apparently its "not ok". so can any1 please help me by sending me a documented code (so i understand). I am kinda on a deadline.

-thank you

``````#include<stdio.h>
#include<conio.h>
#include<iostream>
#include <alloc.h>
#include<graphics.h>

//The 3x3 matrix
struct board
{
int a[3][3],zero_i,zero_j;
struct board *next;
struct board *parent;
}initial,OPEN,CLOSE,SOLUTION;

int count = 1, tcnt=1;

void insertdfs(struct board *,struct board *);
void copy(struct board *,struct board *);
void display(struct board *);

//after the solution is found this function will show all the steps
void show_steps(struct board *s)
{
struct board *temp = s,*temp1;
//count = 0;
SOLUTION.next = NULL;

while(temp->parent!=NULL)
{
temp1 = (struct board*) malloc(sizeof(struct board));
copy(temp,temp1);
insertdfs(temp1,&SOLUTION);
count++;
temp = temp->parent;
}

//getch();
system("cls");
//clrscr();

printf("\nSteps required: %d",count);
temp = SOLUTION.next;

while(temp!=NULL)
{
display(temp);
getch();
temp = temp->next;
}
printf("\nGOAL REACHED...!!");
getch();
}

//Find the zero in the board, so can swap
void find(struct board *s)
{
for(int i=0;i<3;i++)
for(int j=0;j<3;j++)
if(s->a[i][j]==0)
{
s->zero_i = i;
s->zero_j = j;
return;
}
}

// Function will show the matrix while execution
void display(struct board *s)
{
printf("\n");
for(int i=0;i<3;i++)
{
for(int j=0;j<3;j++)
printf("%d",s->a[i][j]);
printf("\n");
}
}

// check if this is the solution
int check(struct board *s)
{
if(s->a[0][0]==1 && s->a[0][1]==2 && s->a[0][2]==3 &&
s->a[1][0]==4 && s->a[1][1]==5 && s->a[1][2]==6 &&
s->a[2][0]==7 && s->a[2][1]==8 && s->a[2][2]==0 )
{
display(s);
printf("Found Solution:- \n");
show_steps(s);
getch();
while(1)
{
continue;
}
return 0;
}
else
{
//count++;
return 1;
}
}

//function to go back to the parent node, means by copying
void copy(struct board *s, struct board *b)
{
for(int i=0;i<3;i++)
{
for(int j=0;j<3;j++)
{
b->a[i][j] = s->a[i][j];
}
}
b->zero_i = s->zero_i;
b->zero_j = s->zero_j;
b->next = NULL;
b->parent = s->parent;
}

int istraversed(struct board *s)
{
struct board *temp = &CLOSE;
while(temp->next!=NULL)
{
for(int i=0;i<3;i++)
{
for(int j=0;j<3;j++)
{
if(s->a[i][j] != temp->a[i][j])
{
goto skip;
}
}
}
goto found;
skip:
temp = temp->next;
}
goto ret;
found: return 1;
ret: return 0;
}

int isvalid(struct board *s,int c)
{

{
if(c==5)
{
if(s->zero_i==2)
{
return 0;
}
else
{
return 1;
}
}
if(c==2)
{

if(s->zero_i==0)
{
return 0;
}
else
{
return 1;
}
}
if(c==1)
{
if(s->zero_j==2)
{
return 0;
}
else
{
return 1;
}
}
if(c==3)
{

if(s->zero_j==0)
{
return 0;
}
else
{
return 1;
}
}
}
return 0;
}

void insertdfs(struct board *s, struct board *b)
{
if(b->next == NULL)
{
b->next = s;
}
else
{
struct board *tmp = b->next;
b->next = s;
s->next = tmp;
}
}

void remove(struct board *s)
{
struct board *tmp = s->next;
OPEN.next = tmp;
s->next = NULL;
insertdfs(s,&CLOSE);
}

// the main function
main()
{
char ip[10];
//clrscr();
printf("\nEnter initial array:\n");
for(int i=0;i<3;i++)
for(int j=0;j<3;j++)
{
again:
scanf("%d",&initial.a[i][j]);
if(initial.a[i][j] >8 || initial.a[i][j] <0)
{       printf("enter a valid input 0 - 8 \n");
goto again;
}
}

int c;
//clrscr();
find(&initial);
struct board *temp,*temp1,t,*tt;
temp = (struct board*) malloc(sizeof(struct board));
//printf("\nGame starts now:-");
initial.next = NULL;
initial.parent = NULL;
copy(&initial,temp);
temp->parent = &OPEN;
OPEN.next = NULL;
OPEN.parent = NULL;
CLOSE.next = NULL;
insertdfs(temp,&OPEN);
while(OPEN.next!=NULL && check(OPEN.next))
{
copy(OPEN.next,&t);
int flag=1,k;
tt=OPEN.next;
remove(OPEN.next);
display(&t);
//getch();
if(isvalid(&t,5))    //UP
{
temp1 = (struct board*) malloc(sizeof(struct board));
copy(&t,temp1);
temp1->a[temp1->zero_i][temp1->zero_j] = temp1->a[temp1->zero_i+1][temp1->zero_j];
temp1->a[temp1->zero_i+1][temp1->zero_j] = 0;
temp1->zero_i++;
temp1->parent = tt;
k=istraversed(temp1);
if(k==0)
{
insertdfs(temp1,&OPEN);
flag=0;
}
}
if(isvalid(&t,1))   //LEFT
{
temp1 = (struct board*) malloc(sizeof(struct board));
copy(&t,temp1);
temp1->a[temp1->zero_i][temp1->zero_j] = temp1->a[temp1->zero_i][temp1->zero_j+1];
temp1->a[temp1->zero_i][temp1->zero_j+1] = 0;
temp1->zero_j++;
temp1->parent = tt;
k=istraversed(temp1);
if(k==0)
{
insertdfs(temp1,&OPEN);
flag=0;
}

}
if(isvalid(&t,2))    //DOWN
{
temp1 = (struct board*) malloc(sizeof(struct board));
copy(&t,temp1);
temp1->a[temp1->zero_i][temp1->zero_j] = temp1->a[temp1->zero_i-1][temp1->zero_j];
temp1->a[temp1->zero_i-1][temp1->zero_j] = 0;
temp1->zero_i--;
temp1->parent = tt;
k=istraversed(temp1);
if(k==0)
{
insertdfs(temp1,&OPEN);
flag=0;
}

}
if(isvalid(&t,3))     //RIGHT
{
temp1 = (struct board*) malloc(sizeof(struct board));
copy(&t,temp1);
temp1->a[temp1->zero_i][temp1->zero_j] = temp1->a[temp1->zero_i][temp1->zero_j-1];
temp1->a[temp1->zero_i][temp1->zero_j-1] = 0;
temp1->zero_j--;
k=istraversed(temp1);
temp1->parent = tt;
if(k==0)
{
insertdfs(temp1,&OPEN);
flag=0;
}

}
if(flag==1)
{
printf("\nNo successor generated...!");
}
}
}
``````

Please narrow down how this is "not ok". What kind of errors or misbehaviours do you get? Please be as specific as possible. What are the rules of the game and how does your program not follow them?

Avoid the use of `goto` in your code. Examine the keywords `break` and `continue` in its place. `scanf()` can get caught in a loop of invalid data; if someone enters a letter when `scanf()` is expecting digits, the input function will leave the unexpected letters on the input queue and never get beyond them. Try reading a line with `fgets()` and then analyse the line with `fscanf()`. In C, it is best to declare your variables at the beginning of the function; it makes it easier to find your variables all together at the top, thus easier to maintain. Place more comments throughout your code to explain what your program is doing and why, at each step along the way.

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