From f014a0ee6a6a5527e851e7b7e1cd096d688492f0 Mon Sep 17 00:00:00 2001
From: arielherself <arielherself@duck.com>
Date: Tue, 17 Dec 2024 19:02:09 +0800
Subject: [PATCH] Add string/sam.cc

---
 string/sam.cc | 73 +++++++++++++++++++++++++++++++++++++++++++++++++++
 template.cc   |  2 +-
 2 files changed, 74 insertions(+), 1 deletion(-)
 create mode 100644 string/sam.cc

diff --git a/string/sam.cc b/string/sam.cc
new file mode 100644
index 0000000..b6754a7
--- /dev/null
+++ b/string/sam.cc
@@ -0,0 +1,73 @@
+template <size_t N>
+struct SAM {
+    vector<int> fa, len;
+    vector<bool> cloned;
+    vector<int> cnt;
+    vector<array<int, N>> ch;
+    int last;
+    int tot;
+
+    int create(int _fa, int _len, bool _cloned, array<int, N>&& _ch) {
+        fa.emplace_back(_fa);
+        len.emplace_back(_len);
+        cloned.emplace_back(_cloned);
+        ch.emplace_back(_ch);
+        return tot++;
+    }
+
+    SAM(void) : fa(2), len(2), cloned(2), ch(2), last(1), tot(2) {}
+
+    void push_back(size_t c) {
+        int p = last;
+        int nw = create(0, len[p] + 1, false, {});
+
+        while (p != 0 and ch[p][c] == 0) {
+            ch[p][c] = nw;
+            p = fa[p];
+        }
+
+        if (p == 0) {
+            fa[nw] = 1;
+        } else {
+            int q = ch[p][c];
+            if (len[q] == len[p] + 1) {
+                fa[nw] = q;
+            } else {
+                int nq = create(fa[q], len[p] + 1, true, array(ch[q]));
+                fa[nw] = fa[q] = nq;
+                while (p != 0 and ch[p][c] == q) {
+                    ch[p][c] = nq;
+                    p = fa[p];
+                }
+            }
+        }
+
+        last = nw;
+    }
+
+    template <typename T>
+    optional<int> find(const basic_string<T>& seq) {
+        int p = 1;
+        for (auto&& c : seq) {
+            if (ch[p][c] == 0) {
+                return nullopt;
+            }
+            p = ch[p][c];
+        }
+        return p;
+    }
+
+    // Fill `cnt` with the number of occurrences of each substring.
+    void populate(void) {
+        cnt.assign(tot, 0);
+        vector<int> idx(tot);
+        iota(idx.begin(), idx.end(), 0);
+        sort_by_key(idx.begin(), idx.end(), expr(len[i], auto&& i), greater());
+        for (auto&& v : idx) {
+            if (v > 1 and not cloned[v]) {
+                cnt[v] += 1;
+            }
+            cnt[fa[v]] += cnt[v];
+        }
+    }
+};
diff --git a/template.cc b/template.cc
index e98d7c7..35a98ad 100644
--- a/template.cc
+++ b/template.cc
@@ -173,7 +173,7 @@ template <typename T, typename Iterator> pair<size_t, unordered_map<T, size_t, s
 /* io */
 #define untie __AS_PROCEDURE(ios_base::sync_with_stdio(0), cin.tie(NULL))
 
-// add declarations to avoid cyclic dependency
+// add declarations to avoid circular dependency
 template<typename T, typename U> istream& operator>>(istream&, pair<T, U>&);
 template<typename T, typename U> ostream& operator<<(ostream&, const pair<T, U>&);
 template<typename T, size_t N> istream& operator>>(istream&, array<T, N>&);