Trie and Suffix tree

// A C program to implement Ukkonen's Suffix Tree Construction
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#define MAX_CHAR 256

struct SuffixTreeNode {
  struct SuffixTreeNode *children[MAX_CHAR];
  //pointer to other node via suffix link
  struct SuffixTreeNode *suffixLink;
  /*(start, end) interval specifies the edge, by which the
    node is connected to its parent node. Each edge will
    connect two nodes,  one parent and one child, and
    (start, end) interval of a given edge  will be stored
    in the child node. Lets say there are two nods A and B
    connected by an edge with indices (5, 8) then this
    indices (5, 8) will be stored in node B. */
  int start;
  int *end;
  /*for leaf nodes, it stores the index of suffix for
    the path from root to leaf*/
  int suffixIndex;
};

typedef struct SuffixTreeNode Node;

char text[100]; //Input string
Node *root = NULL; //Pointer to root node

/*lastNewNode will point to newly created internal node,
  waiting for it's suffix link to be set, which might get
  a new suffix link (other than root) in next extension of
  same phase. lastNewNode will be set to NULL when last
  newly created internal node (if there is any) got it's
  suffix link reset to new internal node created in next
  extension of same phase. */
Node *lastNewNode = NULL;
Node *activeNode = NULL;

/*activeEdge is represeted as input string character
  index (not the character itself)*/
int activeEdge = -1;
int activeLength = 0;

// remainingSuffixCount tells how many suffixes yet to
// be added in tree
int remainingSuffixCount = 0;
int leafEnd = -1;
int *rootEnd = NULL;
int *splitEnd = NULL;
int size = -1; //Length of input string

Node *newNode(int start, int *end) {
  Node *node =(Node*) malloc(sizeof(Node));
  int i;
  for (i = 0; i < MAX_CHAR; i++)
    node->children[i] = NULL;
  /* For root node, suffixLink will be set to NULL
    For internal nodes, suffixLink will be set to root
    by default in  current extension and may change in
    next extension */
  node->suffixLink = root;
  node->start = start;
  node->end = end;
  /* suffixIndex will be set to -1 by default and
    actual suffix index will be set later for leaves
    at the end of all phases */
  node->suffixIndex = -1;
  return node;
}

int edgeLength(Node *n) {
  return *(n->end) - (n->start) + 1;
}

int walkDown(Node *currNode) {
  /*activePoint change for walk down using
    Skip/Count Trick (Trick 1). If activeLength is greater
    than current edge length, set next  internal node as
    activeNode and adjust activeEdge and activeLength
    accordingly to represent same activePoint*/
  if (activeLength >= edgeLength(currNode)) {
    activeEdge += edgeLength(currNode);
    activeLength -= edgeLength(currNode);
    activeNode = currNode;
    return 1;
  }
  return 0;
}

void extendSuffixTree(int pos) {
  /*Extension Rule 1, this takes care of extending all
    leaves created so far in tree*/
  leafEnd = pos;

  /*Increment remainingSuffixCount indicating that a
    new suffix added to the list of suffixes yet to be
    added in tree*/
  remainingSuffixCount++;

  /*set lastNewNode to NULL while starting a new phase,
    indicating there is no internal node waiting for
    it's suffix link reset in current phase*/
  lastNewNode = NULL;

  //Add all suffixes (yet to be added) one by one in tree
  while (remainingSuffixCount > 0) {
    if (activeLength == 0)
      activeEdge = pos;
    // There is no outgoing edge starting with
    // activeEdge from activeNode
    if (activeNode->children[text[activeEdge]] == NULL) {
      //Extension Rule 2 (A new leaf edge gets created)
      activeNode->children[text[activeEdge]] =
          newNode(pos, &leafEnd);
      /*A new leaf edge is created in above line starting
        from an existng node (the current activeNode), and
        if there is any internal node waiting for it's suffix
        link get reset, point the suffix link from that last
        internal node to current activeNode. Then set lastNewNode
        to NULL indicating no more node waiting for suffix link
        reset.*/
      if (lastNewNode != NULL) {
        lastNewNode->suffixLink = activeNode;
        lastNewNode = NULL;
      }
    } else {
      // There is an outgoing edge starting with activeEdge
      // from activeNode
      // Get the next node at the end of edge starting
      // with activeEdge
      Node *next = activeNode->children[text[activeEdge]];
      if (walkDown(next)) { //Do walkdown
        //Start from next node (the new activeNode)
        continue;
      }
      /*Extension Rule 3 (current character being processed
        is already on the edge)*/
      if (text[next->start + activeLength] == text[pos]) {
        //If a newly created node waiting for it's 
        //suffix link to be set, then set suffix link 
        //of that waiting node to curent active node
        if (lastNewNode != NULL && activeNode != root) {
          lastNewNode->suffixLink = activeNode;
          lastNewNode = NULL;
        }
        activeLength++;
        /*STOP all further processing in this phase
          and move on to next phase*/
        break;
      }
      /*We will be here when activePoint is in middle of
        the edge being traversed and current character
        being processed is not on the edge (we fall off
        the tree). In this case, we add a new internal node
        and a new leaf edge going out of that new node. This
        is Extension Rule 2, where a new leaf edge and a new
        internal node get created*/
      splitEnd = (int*) malloc(sizeof(int));
      *splitEnd = next->start + activeLength - 1;
      //New internal node
      Node *split = newNode(next->start, splitEnd);
      activeNode->children[text[activeEdge]] = split;

      //New leaf coming out of new internal node
      split->children[text[pos]] = newNode(pos, &leafEnd);
      next->start += activeLength;
      split->children[text[next->start]] = next;

      /*We got a new internal node here. If there is any
        internal node created in last extensions of same
        phase which is still waiting for it's suffix link
        reset, do it now.*/
      if (lastNewNode != NULL) {
        /*suffixLink of lastNewNode points to current newly
          created internal node*/
        lastNewNode->suffixLink = split;
      }
      /*Make the current newly created internal node waiting
        for it's suffix link reset (which is pointing to root
        at present). If we come across any other internal node
        (existing or newly created) in next extension of same
        phase, when a new leaf edge gets added (i.e. when
        Extension Rule 2 applies is any of the next extension
        of same phase) at that point, suffixLink of this node
        will point to that internal node.*/
      lastNewNode = split;
    }
    /* One suffix got added in tree, decrement the count of
       suffixes yet to be added.*/
    remainingSuffixCount--;
    if (activeNode == root && activeLength > 0) {
      /* Rule 1*/
      activeLength--;
      activeEdge = pos - remainingSuffixCount + 1;
    } else if (activeNode != root) {
      /* Rule 3 */
      activeNode = activeNode->suffixLink;
    }
  }
}

void print(int i, int j)
{
  int k;
  for (k=i; k<=j; k++)
    printf("%c", text[k]);
}

//Print the suffix tree as well along with setting suffix index
//So tree will be printed in DFS manner
//Each edge along with it's suffix index will be printed
void setSuffixIndexByDFS(Node *n, int labelHeight)
{
  if (n == NULL)  return;

  if (n->start != -1) {
    //A non-root node
    //Print the label on edge from parent to current node
    print(n->start, *(n->end));
  }
  int leaf = 1;
  int i;
  for (i = 0; i < MAX_CHAR; i++) {
    if (n->children[i] != NULL) {
      if (leaf == 1 && n->start != -1)
        printf(" [%d]\n", n->suffixIndex);
      //Current node is not a leaf as it has outgoing
      //edges from it.
      leaf = 0;
      setSuffixIndexByDFS(n->children[i], labelHeight +
                          edgeLength(n->children[i]));
    }
  }
  if (leaf == 1) {
    n->suffixIndex = size - labelHeight;
    printf(" [%d]\n", n->suffixIndex);
  }
}

void freeSuffixTreeByPostOrder(Node *n)
{
  if (n == NULL)
    return;
  int i;
  for (i = 0; i < MAX_CHAR; i++) {
    if (n->children[i] != NULL) {
      freeSuffixTreeByPostOrder(n->children[i]);
    }
  }
  if (n->suffixIndex == -1)
    free(n->end);
  free(n);
}

/*Build the suffix tree and print the edge labels along with
  suffixIndex. suffixIndex for leaf edges will be >= 0 and
  for non-leaf edges will be -1*/
void buildSuffixTree() {
  size = strlen(text);
  int i;
  rootEnd = (int*) malloc(sizeof(int));
  *rootEnd = - 1;
  /*Root is a special node with start and end indices as -1,
    as it has no parent from where an edge comes to root*/
  root = newNode(-1, rootEnd);

  activeNode = root; //First activeNode will be root
  for (i = 0; i < size; i++)
    extendSuffixTree(i);
  int labelHeight = 0;
  setSuffixIndexByDFS(root, labelHeight);
  //Free the dynamically allocated memory
  freeSuffixTreeByPostOrder(root);
}

// driver program to test above functions
int main(int argc, char *argv[]) {
  //  strcpy(text, "abc"); buildSuffixTree();
  //  strcpy(text, "xabxac#");    buildSuffixTree();
  //  strcpy(text, "xabxa");  buildSuffixTree();
  //  strcpy(text, "xabxa$"); buildSuffixTree();
  strcpy(text, "abcabxabcd$"); buildSuffixTree();
  //  strcpy(text, "geeksforgeeks$"); buildSuffixTree();
  //  strcpy(text, "THIS IS A TEST TEXT$"); buildSuffixTree();
  //  strcpy(text, "AABAACAADAABAAABAA$"); buildSuffixTree();
  return 0;
}