c++ - Why does my function(on binary tree) print an unexpected result? -

i wanna make function , takes parametrs binary tree ,t, , 2 integers a,b , prints how many integers between , b...

as example here binary tree ,with 3 nodes , data : 10,15,20. call function example : between(t ,10 ,20) , result expect number 1 , not happen.. function :

   ` int between (tree t, int a, int b) {     if (t== null)         return 0;     if ((t->data >a ) && ( t->data <b))        return 1 + between(t->left,a,b) + between(t->right,a,b); } 

can explain me ?

first of all, if number not between , b, have not defined return value, error other program doesnt required, function doesnt return int value.

secondly, should go on, when value not on range. function should this:

int between (tree t, int a, int b) {     if (t== null)         return 0;     if ((t->data >a ) && ( t->data <b))        return 1 + between(t->left,a,b) + between(t->right,a,b);     else return between(t->left,a,b) + between(t->right,a,b);  } 

better yet, if values on left lower values on right (search tree) can make improvement.

int between (tree t, int a, int b) {     if (t== null)         return 0;     if ((t->data >a ) && ( t->data <b))        return 1 + between(t->left,a,b) + between(t->right,a,b);     else if(t->data<a)           return between(t->right,a,b);     else if(t->data>b)          return between(t->left,a,b); }