Given the Infix and Postfix traversal, construct the tree

Given the Infix and Postfix traversal, construct the tree

Answer:
Possible only in cases where there are unique elements.

/**
 * Program to construct a tree from a Infix and prefix traversals.
 * */
#include 
using namespace std;

struct TreeNode
{
    char node;
    TreeNode *left;
    TreeNode *right;
    TreeNode(char ch)
    {
        this->node = ch;
        this->left = 0;
        this->right = 0;
    }
};
template 
TreeNode* CtorTree(RandIter infix_begin, RandIter infix_end, RandIter postfix_begin, RandIter postfix_end)
{
    /* Nothing to add */
    if( (infix_begin == infix_end) || (postfix_begin == postfix_end) )
        return NULL;
    /* The current element in the postfix becomes the root */
    TreeNode *tnode = new TreeNode(*postfix_begin);
    /* Search for the root in infix representation from reverse */
    RandIter j = infix_end;
    while( j>= infix_begin )
    {
        --j;
        if (*j == *postfix_begin)
            break;
    }
    ptrdiff_t num_nodes = j - infix_begin;
    ++postfix_begin;

    /* we have found the corresponding root at location j */
    TreeNode *left_subtree = CtorTree(infix_begin, j, postfix_begin , postfix_begin + num_nodes);
    TreeNode *right_subtree = CtorTree(j+1, infix_end, postfix_begin + num_nodes , postfix_end );
    tnode->left = left_subtree;
    tnode->right = right_subtree;
    return tnode;
}

void Infix_traversal(TreeNode* n)
{
    if (n)
    {
        Infix_traversal(n->left);
        cout << n->node;
        Infix_traversal(n->right);
    }
}

int main(int argc, char ** argv)
{
    if ( argc != 3 )
    {
        cerr << "Usage:" << argv[0] << " infix prefix " << endl;
    }
    else
    {
        char *infix = strdup(argv[1]);
        char *prefix = strdup(argv[2]);
        TreeNode *tree = CtorTree(infix, infix+strlen(infix), prefix, prefix + strlen(prefix));
        cout << endl << "The Infix traversal of the constructed tree : " << endl;
        Infix_traversal (tree);
        free (infix);
        free (prefix);
    }
    return 0;
}