How to print all possible balanced parentheses for an expression?

Question

For example, with elements a,b,c,d, there are 5 possible ways to take neighboring elements and reduce them into a single element, where exactly two elements mus

Answer 1

And, here is some C++ code for the same :

bool is_a_solution( string partial,int n,int k) { 
if(partial.length() == n*2 )  
 return true;
return false;
  }
string constructCandidate(int n,string input,string partial, int k) { 
int xcount=0,ycount=0;
int count;
int i;
string candi;
if(k == 0)  
    return string("(");
else { 
    for(i=0;i