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Copy pathsuffix_tree.cc
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137 lines (124 loc) · 3.14 KB
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//
// Suffix Tree (Ukkonen's algorithm)
//
// Description:
// A suffix tree of a given string s is a
// patricia (i.e., compressed trie) of all suffixes of s.
//
// Algorithm:
// Ukkonen's left-to-right scan algorithm.
// See the original paper.
//
// Complexity:
// O(n).
// Due to a large constant factor, it is useful in
// n <= 10000 in programming contest.
// Use suffix array, instead of suffix tree.
//
// References:
// E. Ukkonen (1995):
// On-line Construction of Suffix Trees.
// Algorithmica, vol.14, no.3, pp.249--260.
#include <iostream>
#include <vector>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <functional>
using namespace std;
#define fst first
#define snd second
#define all(c) ((c).begin()), ((c).end())
struct suffix_tree {
const char *str;
const int n;
int root;
struct edge { int to, a, b; };
vector<vector<edge>> adj;
vector<int> suf;
int add_node() {
adj.push_back(vector<edge>(0x100, {-1}));
suf.push_back(0);
return suf.size()-1;
}
int add_edge(int r, const edge &e) {
adj[r][str[e.a]] = e;
}
int test_and_split(int s, int k, int p, char c) {
if (k > p) return adj[s][c].to == -1 ? s : 0;
edge e = adj[s][str[k]];
if (c == str[e.a + p - k + 1]) return 0;
int r = add_node();
add_edge(r, {e.to, e.a + p - k + 1, e.b});
add_edge(s, {r, e.a, e.a + p - k});
return r;
}
int canonize(int s, int &k, int p) {
if (p < k) return s;
if (s == 0) { s = root; ++k; if (p < k) return s; }
edge e = adj[s][str[k]];
while (e.b - e.a <= p - k) {
k = k + e.b - e.a + 1;
s = e.to;
if (k <= p) e = adj[s][str[k]];
}
return s;
}
int update(int s, int &k, int i) {
int oldr = root, r = test_and_split(s, k, i-1, str[i]);
while (r) {
int rp = add_node();
add_edge(r, {rp, i, n-1});
if (oldr != root) suf[oldr] = r;
oldr = r;
s = canonize(suf[s], k, i-1);
r = test_and_split(s, k, i-1, str[i]);
}
if (oldr != root) suf[oldr] = s;
return s;
}
suffix_tree(const char *str) : str(str), n(strlen(str)) {
add_node(); // bottom = 0
root = add_node();
int s = root, k = 0;
for (int i = 0; i < n; ++i) {
s = update(s, k, i);
s = canonize(s, k, i);
}
}
void display(int s, int tab = 0) {
if (s == -1 || s == 0) return;
for (int c = 0; c < 0x100; ++c) {
if (adj[s][c].to != -1) {
cout << string(tab, ' ');
for (int i = adj[s][c].a; i <= adj[s][c].b; ++i)
cout << str[i];
cout << endl;
display(adj[s][c].to, tab+2);
}
}
}
void display() { display(root); }
};
// === tick a time ===
#include <ctime>
double tick() {
static clock_t oldtick;
clock_t newtick = clock();
double diff = 1.0*(newtick - oldtick) / CLOCKS_PER_SEC;
oldtick = newtick;
return diff;
}
int main() {
//suffix_tree T("abracadabra");
//suffix_tree T("abracadabra");
//suffix_tree T("AAAAABCDEAAAAA#");
const int n = 10000;
char s[n+1];
for (int i = 0; i < n; ++i)
s[i] = "abc"[rand() % 3];
tick();
suffix_tree T(s);
cout << "construction: " << tick() << endl;
//T.display();
}