Question

I declared an array and take input from user. Now i want to check duplicate entries, they have to be deleted and memory should be freed. Is it possible to free memory.

freeing the unused memory and reducing the array size?

I entered [10,21,3,4,4,2,6,7,21,4,10].it should get truncated as [10,21,3,4,2,6,7] and array length should now be 7,and i don’t want to use sorting.

Answer 1

I declared an array of length 100 and took input from user

so you mean like this:

    int input[100];
/* - ask 100 input from user */

Is it possible to free memory

the answer is no because you statically allocate 100 integers.

If you want to be able to reduce memory then you should do something like this:

int *tempBuffer=malloc(100*sizeof(int)); /* dynamic allocation */

for(i=0;i<100;++i) scanf("%d",&tempBuffer[i]);/* - ask 100 input from user */

int uniqueN=10   /* - assume the first 10 entries are the unique entries */

int *realBuffer=malloc(uniqueN*sizeof(int)); /* - allocate new buffer just enough for the unique entries */

for(i=0;i<uniqueN;++i) realBuffer[i]=tempBuffer[i];  /* - copy the unique entries from input to the final buffer */

free(tempBuffer);  /* - tempBuffer is now unused, free it */

/* here we have realBuffer with just enough size, no unused memory */

Another solution is to realloc tempBuffer after arranging the first uniqueN entries to be the unique entries:

realloc(tempBuffer,uniqueN);

don’t forget to check if malloc or realloc returns NULL