Suffix tree: Difference between revisions
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The computation time for an efficient algorithm should be <math>O(n)</math>, but such an algorithm might be difficult to implement. An easier, <math>O(n^2)</math> algorithm is accepted.
=={{header|D}}==
<lang D>import std.stdio;
struct Node {
string sub = ""; // a substring of the input string
int[] ch; // array of child nodes
this(string sub, int[] children ...) {
this.sub = sub;
ch = children;
}
}
struct SuffixTree {
Node[] nodes;
this(string str) {
nodes ~= Node();
for (int i=0; i<str.length; ++i) {
addSuffix(str[i..$]);
}
}
private void addSuffix(string suf) {
int n = 0;
int i = 0;
while (i < suf.length) {
char b = suf[i];
int x2 = 0;
int n2;
while (true) {
auto children = nodes[n].ch;
if (x2 == children.length) {
// no matching child, remainder of suf becomes new node.
n2 = nodes.length;
nodes ~= Node(suf[i..$]);
nodes[n].ch ~= n2;
return;
}
n2 = children[x2];
if (nodes[n2].sub[0] == b) {
break;
}
x2++;
}
// find prefix of remaining suffix in common with child
auto sub2 = nodes[n2].sub;
int j = 0;
while (j < sub2.length) {
if (suf[i + j] != sub2[j]) {
// split n2
auto n3 = n2;
// new node for the part in common
n2 = nodes.length;
nodes ~= Node(sub2[0..j], n3);
nodes[n3].sub = sub2[j..$]; // old node loses the part in common
nodes[n].ch[x2] = n2;
break; // continue down the tree
}
j++;
}
i += j; // advance past part in common
n = n2; // continue down the tree
}
}
void visualize() {
if (nodes.length == 0) {
writeln("<empty>");
return;
}
void f(int n, string pre) {
auto children = nodes[n].ch;
if (children.length == 0) {
writefln("╴ %s", nodes[n].sub);
return;
}
writefln("┐ %s", nodes[n].sub);
foreach (c; children[0..$-1]) {
write(pre, "├─");
f(c, pre ~ "│ ");
}
write(pre, "└─");
f(children[$-1], pre ~ " ");
}
f(0, "");
}
}
void main() {
SuffixTree("banana$").visualize();
}</lang>
{{out}}
<pre>┐
├─╴ banana$
├─┐ a
│ ├─┐ na
│ │ ├─╴ na$
│ │ └─╴ $
│ └─╴ $
├─┐ na
│ ├─╴ na$
│ └─╴ $
└─╴ $</pre>
=={{header|Go}}==
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