Tree Traversal Coding: How do I code the following in C program?  // ====== BEGIN INSERT FUNCTION DEFS TO WALK TREE ========= // define 3 functions - preorder, inorder, postorder to walk tree, printing out data (char) // associated with each node visited: void preorder (node* np) {} void inorder (node* np) {} void postorder (node* np) {}   walk.c file with the rest of the code given. #include #include #include #include   #define MAX_STRING 200   // ========================== NODE/TREE DEFINITIONS ========================== // define node structure  typedef struct nd {   int data;   struct nd* left;   struct nd* right; } node;   // "new" function to create a node, set data value to d and children to NULL node* newNode(int d) {   node* np;   np = (node*)malloc(sizeof(node));   if (np != NULL) {     np->data = d;     np->left = NULL;     np->right = NULL;   }   return(np); }   // declare root of our binary tree node* rootp = NULL;     // ========================== STRING DEFINITIONS ========================== // dna is a string defining the content and structure of the tree in pre-order with '\n' for NULL pointers char dna[MAX_STRING] = "ABDHP\n\nQ\n\nIR\n\nS\n\nEJT\n\nU\n\nKV\n\nW\n\nCFL\n\nMX\n\nY\n\nGN\nZ\n\nO\n\n";   // remove the first character from string s and return it, \x01 will be an error code if string is empty char getFirstChar(char* s) {   char c;   if (strlen(s) > 0) {     // copy the first character     c = s[0];       // remove the first charcter from the string     memmove(s, s+1, strlen(s));   } else {     // empty string, set error code     c = '\x01';   }   return c; } // ========================== MAIN RECURSIVE FUNCTION TO BUILD TREE  ========================== // using the instruction in string s, insert the defined nodes into tree pointed to by rp void insertNode (node* rp, char* s) {   char c;   // temporary character   // we assume that rp points to an existing node and   // we are going to add its two children based on the next two instructions in s   if (rp != NULL) {     // if instruction string is not empty then add a new node to the left     if (strlen(s) >  0) {       // get the first character of the string which is our "instruction"       c = getFirstChar(s);       if (c == '\x01') {         printf("ILLEGAL CHARACTER IN INSTRUCTION STRING\n");       }         // if instruction does not tell us to insert null, create a new node and add it as left child, recurse       if (c != '\n') {         rp->left = newNode(c);         insertNode(rp->left, s);       }     }       // if instruction string is not empty then add a new node to the right     if (strlen(s) >  0) {       // get the first character of the string which is our "instruction"       c = getFirstChar(s);         if (c == '\x01') {         printf("ILLEGAL CHARACTER IN INSTRUCTION STRING\n");       }         // if instruction does not tell us to insert null, create a new node and add it as right child, recurse       if (c != '\n') {         rp->right = newNode(c);         insertNode(rp->right, s);       }     }   }   return; } // ========================== BEGIN INSERT FUNCTION DEFS TO WALK TREE ========================== // define 3 functions - preorder, inorder, postorder to walk tree, printing out data (char) // associated with each node visited: void preorder (node* np) {}   void inorder (node* np) {}   void postorder (node* np) {}     // ========================== END INSERT FUNCTIONS HERE TO WALK TREE ==========================   // ========================== MAIN PROGRAM  ========================== int main() {   char c; // temporary character variable     // prime the pump - add the first node to the tree and then recursively call on children   rootp = NULL;     // if instruction string is not empty then create root node   if (strlen(dna) >  0) {     // get the first character of the string which is our "instruction"     c = getFirstChar(dna);       if (c == '\x01') {       printf("ILLEGAL CHARACTER IN INSTRUCTION STRING\n");     }       // if instruction does not tell us to insert null, create a new node and add it as left child, recurse     if (c != '\n') {       rootp = newNode(c);       insertNode(rootp, dna);     }   }   // ========================== MAIN PROG CODE TO CALL WALK FUNCTONS  ========================== printf("PREORDER:\n");   preorder(rootp);   printf("\n\n");     printf("INORDER:\n");   inorder(rootp);   printf("\n\n");     printf("POSTORDER:\n");   postorder(rootp);   printf("\n\n");     return 0; }