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Added Suffix Tree Implementation in C++ #261

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Oct 30, 2019
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Added Suffix Tree Implementation in C++ #261

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87 changes: 87 additions & 0 deletions Trees/Suffix Tree
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Original file line number Diff line number Diff line change
@@ -0,0 +1,87 @@
string s;
int n;

struct node {
int l, r, par, link;
map<char,int> next;

node (int l=0, int r=0, int par=-1)
: l(l), r(r), par(par), link(-1) {}
int len() { return r - l; }
int &get (char c) {
if (!next.count(c)) next[c] = -1;
return next[c];
}
};
node t[MAXN];
int sz;

struct state {
int v, pos;
state (int v, int pos) : v(v), pos(pos) {}
};
state ptr (0, 0);

state go (state st, int l, int r) {
while (l < r)
if (st.pos == t[st.v].len()) {
st = state (t[st.v].get( s[l] ), 0);
if (st.v == -1) return st;
}
else {
if (s[ t[st.v].l + st.pos ] != s[l])
return state (-1, -1);
if (r-l < t[st.v].len() - st.pos)
return state (st.v, st.pos + r-l);
l += t[st.v].len() - st.pos;
st.pos = t[st.v].len();
}
return st;
}

int split (state st) {
if (st.pos == t[st.v].len())
return st.v;
if (st.pos == 0)
return t[st.v].par;
node v = t[st.v];
int id = sz++;
t[id] = node (v.l, v.l+st.pos, v.par);
t[v.par].get( s[v.l] ) = id;
t[id].get( s[v.l+st.pos] ) = st.v;
t[st.v].par = id;
t[st.v].l += st.pos;
return id;
}

int get_link (int v) {
if (t[v].link != -1) return t[v].link;
if (t[v].par == -1) return 0;
int to = get_link (t[v].par);
return t[v].link = split (go (state(to,t[to].len()), t[v].l + (t[v].par==0), t[v].r));
}

void tree_extend (int pos) {
for(;;) {
state nptr = go (ptr, pos, pos+1);
if (nptr.v != -1) {
ptr = nptr;
return;
}

int mid = split (ptr);
int leaf = sz++;
t[leaf] = node (pos, n, mid);
t[mid].get( s[pos] ) = leaf;

ptr.v = get_link (mid);
ptr.pos = t[ptr.v].len();
if (!mid) break;
}
}

void build_tree() {
sz = 1;
for (int i=0; i<n; ++i)
tree_extend (i);
}