##
__GENIE SEQUENCE__

Link to the question : KURUK14

###
__HINT :__

It is said that a genie sequence is a sequence of numbers which can be arranged in such a way that they either tell the number of elements behind or number of elements in front of them. In order for a n elements sequence to follow the rule, if it contains c then it should also contain n-c or c, because if at the (c+1)th position we say there are c elements behind it, then at (n-c + 1)th we can say there are n-c elements behind it or c elements in front of it. So either 2 c's or 2 (n-c)'s or 1 c and 1 (n-c) must be present. So in the case of 2 c's or 2 (n-c)'s we make them 1 c and 1 (n-c) then we will get all numbers from 0 to n-1 in the genie sequence. So we just need to check all 0 to n-1 numbers are present or not after converting repeating numbers to n-x form.

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__SOURCE CODE :__

```
/* Genie Sequence - (KURUK 14) */
```

/* Sushant Gupta */

#include<stdio.h>

int main()

{

int t;

scanf("%d",&t);

while(t--)

{

int n,i,f=0,c;

scanf("%d",&n);

int a[n];

for(i=0;i<n;i++)

a[i]= 0;

for(i=0;i<n;i++)

{

scanf("%d",&c);

if(c<n)

{

if(a[c]==0)

a[c]=1;

else

a[n-1-c]=1;

}

}

for(i=0;i<n;i++)

{

if(a[i]==0)

f=1;

}

if(f==0)

printf("YES\n");

else

printf("NO\n");

}

return 0;

}

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