Compilation Error using Custom Sort inside Class

Question

I am trying to use custom sort inside a class, such as sort(arr,arr+n,cust); inside a class function. Custom sort looks like this:

bool cust (int a, int b) {
  return pos[a]<pos[b];
}

Where pos is an array inside class. But it does not compile, and gives compilation error

"invalid use of non-static member function" how to get rid of compilation error.

my code -> https://pastebin.com/W1zw0A5s

I have tried writing:

static bool cust (int a, int b) {
     /* same code */
} 

which hasn't helped.

Answer 1

According to the pastebin link, this function is a member function in your class. You need to bind the this pointer to it in order to use it:

sort(sa,sa+n, [this](int a, int b){ return this->sufCmp(a,b); } );