EP 07 - prefix, infix & postfix

#include <stdio.h>
#include <stdlib.h>

#define MAX 1000

typedef struct TreeNode {
	char letter;
	struct TreeNode *right;
	struct TreeNode *left;
} TreeNode;

TreeNode* NewNode (char letter);
void ShowPosfix (TreeNode *tree);
int Src (char *str, int begin, int end, char letter);
TreeNode* Tree (char *infix, char *prefix, int inBegin, int inEnd);

short k;

int main() {
	short casesQtt;
	short nodesQtt, i;
	char prefix[MAX], infix[MAX];

	scanf("%hu", &casesQtt);

	while (casesQtt--) {
		scanf ("%hu %s %s%*c", &nodesQtt, prefix, infix);
		k = 0;
		TreeNode *root = Tree (infix, prefix, 0, nodesQtt-1);
		ShowPosfix (root);
		printf ("\n");
	}
}

TreeNode* NewNode (char letter) {
	TreeNode *node = (TreeNode *) malloc (sizeof(TreeNode));
	node->letter = letter;
	node->left = node->right = NULL;

	return node;
}

int Src (char *str, int begin, int end, char letter) {
	short i;
  
	for (i = begin; i <= end; ++i) {
		if (str[i] == letter)
			return i;
  }

	return -1;
}

TreeNode* Tree (char *infix, char *prefix, int inBegin, int inEnd) {
	int infix_k;

	if (inBegin > inEnd)
		return NULL;

	TreeNode *node = NewNode (prefix[k++]);
	if (inBegin == inEnd)
		return node;

	infix_k = Src (infix, inBegin, inEnd, node->letter);
	node->left = Tree (infix, prefix, inBegin, infix_k-1);
	node->right = Tree (infix, prefix, infix_k+1, inEnd);

	return node;
}

void ShowPosfix (TreeNode *node) {
	if (!node)
		return;

	ShowPosfix (node->left);
	ShowPosfix (node->right);
	printf ("%c", node->letter);
}