c - Error in implementation of a stack with O(1) find-max/find-min? -

i have implemented several functions stack adt. trying find max , min values in o(1) time , have augmented stack structure serve purpose. code:

 void mms_push(mmstack mms, int i) {  struct llnode *new = malloc(sizeof(struct llnode)); new->item = i; if(mms->len!=0) {  new->next = mms->topnode;  mms->topnode = new; } else  {  new->next = null;  mms->topnode = new; }  if (mms->len == 0) { mms->topnode->minc = i; mms->topnode->maxc = i;} else {   if(mms->topnode->maxc < i)   {       mms->topnode->maxc = i;   }    if(i<mms->topnode->minc)   {       mms->topnode->minc = i;   }   mms->len++;}   int mms_pop(mmstack mms) {   assert(mms);   int ret = mms->topnode->item;   struct llnode *backup = mms->topnode;   mms->topnode = mms->topnode->next;   mms->len--;     free(backup);   return ret; } 

my structures used below:

struct llnode {    int item;   struct llnode *next;   int minc;   int maxc; };  struct mmstack {   int len ;   struct llnode *topnode;  };   typedef struct mmstack *mmstack; 

i not getting correct value of max , min values. how correct code right value of max , min element in stack?

thanks in advance!

take @ code:

if (mms->len == 0) {   mms->topnode->minc = i;   mms->topnode->maxc = i; } else {   if(mms->topnode->maxc < i)   {       mms->topnode->maxc = i;   }    if(i<mms->topnode->minc)   {       mms->topnode->minc = i;   } } 

notice in else branch, you're reading values of mms->topnode->minc , mms->topnode->maxc before you've initialized them. think meant @ values of mms->topnode->minc/maxc before reassigned mms->topnode. fix this, try doing this:

else {   mms->topnode->maxc = mms->topnode->next->maxc;   mms->topnode->minc = mms->topnode->next->minc;    if(mms->topnode->maxc < i)   {       mms->topnode->maxc = i;   }    if(i<mms->topnode->minc)   {       mms->topnode->minc = i;   } } 

these 2 lines initialize min , max values old max values before comparing against i, should ensure value.

hope helps!