#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#define MAX_CHAR 256
struct
SuffixTreeNode {
struct
SuffixTreeNode *children[MAX_CHAR];
struct
SuffixTreeNode *suffixLink;
int
start;
int
*end;
int
suffixIndex;
};
typedef
struct
SuffixTreeNode Node;
char
text[100];
Node *root = NULL;
Node *lastNewNode = NULL;
Node *activeNode = NULL;
int
activeEdge = -1;
int
activeLength = 0;
int
remainingSuffixCount = 0;
int
leafEnd = -1;
int
*rootEnd = NULL;
int
*splitEnd = NULL;
int
size = -1;
int
size1 = 0;
Node *newNode(
int
start,
int
*end) {
Node *node = (Node*)
malloc
(
sizeof
(Node));
for
(
int
i = 0; i < MAX_CHAR; i++) {
node->children[i] = NULL;
}
node->suffixLink = root;
node->start = start;
node->end = end;
node->suffixIndex = -1;
return
node;
}
int
edgeLength(Node *n) {
if
(n == root) {
return
0;
}
return
*(n->end) - (n->start) + 1;
}
int
walkDown(Node *currNode) {
if
(activeLength >= edgeLength(currNode)) {
activeEdge += edgeLength(currNode);
activeLength -= edgeLength(currNode);
activeNode = currNode;
return
1;
}
return
0;
}
void
extendSuffixTree(
int
pos) {
leafEnd = pos;
remainingSuffixCount++;
lastNewNode = NULL;
while
(remainingSuffixCount > 0) {
if
(activeLength == 0) {
activeEdge = pos;
}
if
(activeNode->children[(unsigned
char
) text[activeEdge]] == NULL) {
activeNode->children[(unsigned
char
) text[activeEdge]] = newNode(pos, &leafEnd);
if
(lastNewNode != NULL) {
lastNewNode->suffixLink = activeNode;
lastNewNode = NULL;
}
}
else
{
Node *next = activeNode->children[(unsigned
char
) text[activeEdge]];
if
(walkDown(next)) {
continue
;
}
if
(text[next->start + activeLength] == text[pos]) {
if
(lastNewNode != NULL && activeNode != root) {
lastNewNode->suffixLink = activeNode;
lastNewNode = NULL;
}
activeLength++;
break
;
}
splitEnd = (
int
*)
malloc
(
sizeof
(
int
));
*splitEnd = next->start + activeLength - 1;
Node *split = newNode(next->start, splitEnd);
activeNode->children[(unsigned
char
) text[next->start]] = split;
split->children[(unsigned
char
) text[pos]] = newNode(pos, &leafEnd);
next->start += activeLength;
split->children[(unsigned
char
) text[next->start]] = next;
if
(lastNewNode != NULL) {
lastNewNode->suffixLink = split;
}
lastNewNode = split;
}
remainingSuffixCount--;
if
(activeNode == root && activeLength > 0) {
activeLength--;
activeEdge = pos - remainingSuffixCount + 1;
}
else
if
(activeNode != root) {
activeNode = activeNode->suffixLink;
}
}
}
void
print(
int
i,
int
j)
{
int
k;
for
(k = i; k <= j && text[k] !=
'#'
; k++)
printf
(
"%c"
, text[k]);
if
(k <= j)
printf
(
"#"
);
}
void
setSuffixIndexByDFS(Node *n,
int
labelHeight)
{
if
(n == NULL)
return
;
if
(n->start != -1)
{
}
int
leaf = 1;
int
i;
for
(i = 0; i < MAX_CHAR; i++)
{
if
(n->children[i] != NULL)
{
leaf = 0;
setSuffixIndexByDFS(n->children[i], labelHeight +
edgeLength(n->children[i]));
}
}
if
(leaf == 1)
{
for
(i = n->start; i <= *(n->end); i++)
{
if
(text[i] ==
'#'
)
{
n->end = (
int
*)
malloc
(
sizeof
(
int
));
*(n->end) = i;
}
}
n->suffixIndex = size - labelHeight;
}
}
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);
}
void
buildSuffixTree()
{
size =
strlen
(text);
int
i;
rootEnd = (
int
*)
malloc
(
sizeof
(
int
));
*rootEnd = - 1;
root = newNode(-1, rootEnd);
activeNode = root;
for
(i = 0; i < size; i++)
extendSuffixTree(i);
int
labelHeight = 0;
setSuffixIndexByDFS(root, labelHeight);
}
int
doTraversal(Node *n,
int
labelHeight,
int
* maxHeight,
int
* substringStartIndex)
{
if
(n == NULL)
{
return
0;
}
int
i = 0;
int
ret = -1;
if
(n->suffixIndex < 0)
{
for
(i = 0; i < MAX_CHAR; i++)
{
if
(n->children[i] != NULL)
{
ret = doTraversal(n->children[i], labelHeight +
edgeLength(n->children[i]),
maxHeight, substringStartIndex);
if
(n->suffixIndex == -1)
n->suffixIndex = ret;
else
if
((n->suffixIndex == -2 && ret == -3) ||
(n->suffixIndex == -3 && ret == -2) ||
n->suffixIndex == -4)
{
n->suffixIndex = -4;
if
(*maxHeight < labelHeight)
{
*maxHeight = labelHeight;
*substringStartIndex = *(n->end) -
labelHeight + 1;
}
}
}
}
}
else
if
(n->suffixIndex > -1 && n->suffixIndex < size1)
return
-2;
else
if
(n->suffixIndex >= size1)
return
-3;
return
n->suffixIndex;
}
void
getLongestCommonSubstring()
{
int
maxHeight = 0;
int
substringStartIndex = 0;
doTraversal(root, 0, &maxHeight, &substringStartIndex);
int
k;
for
(k = 0; k < maxHeight; k++)
printf
(
"%c"
, text[k + substringStartIndex]);
if
(k == 0)
printf
(
"No common substring"
);
else
printf
(
", of length: %d"
, maxHeight);
printf
(
"\n"
);
}
int
main(
int
argc,
char
*argv[])
{
size1 = 7;
printf
(
"Longest Common Substring in xabxac and abcabxabcd is: "
);
strcpy
(text,
"xabxac#abcabxabcd$"
); buildSuffixTree();
getLongestCommonSubstring();
freeSuffixTreeByPostOrder(root);
size1 = 10;
printf
(
"Longest Common Substring in xabxaabxa and babxba is: "
);
strcpy
(text,
"xabxaabxa#babxba$"
); buildSuffixTree();
getLongestCommonSubstring();
freeSuffixTreeByPostOrder(root);
size1 = 14;
printf
(
"Longest Common Substring in GeeksforGeeks and GeeksQuiz is: "
);
strcpy
(text,
"GeeksforGeeks#GeeksQuiz$"
); buildSuffixTree();
getLongestCommonSubstring();
freeSuffixTreeByPostOrder(root);
size1 = 26;
printf
(
"Longest Common Substring in OldSite:GeeksforGeeks.org"
);
printf
(
" and NewSite:GeeksQuiz.com is: "
);
strcpy
(text,
"OldSite:GeeksforGeeks.org#NewSite:GeeksQuiz.com$"
);
buildSuffixTree();
getLongestCommonSubstring();
freeSuffixTreeByPostOrder(root);
size1 = 6;
printf
(
"Longest Common Substring in abcde and fghie is: "
);
strcpy
(text,
"abcde#fghie$"
); buildSuffixTree();
getLongestCommonSubstring();
freeSuffixTreeByPostOrder(root);
size1 = 6;
printf
(
"Longest Common Substring in pqrst and uvwxyz is: "
);
strcpy
(text,
"pqrst#uvwxyz$"
); buildSuffixTree();
getLongestCommonSubstring();
freeSuffixTreeByPostOrder(root);
return
0;
}