From 0018dbf69f7212f5440788599557479535405598 Mon Sep 17 00:00:00 2001
From: subcrip <contact@subc.rip>
Date: Wed, 10 Apr 2024 13:53:42 +0800
Subject: [PATCH] Add string/slice_hash.cc

---
 string/slice_hash.cc | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)
 create mode 100644 string/slice_hash.cc

diff --git a/string/slice_hash.cc b/string/slice_hash.cc
new file mode 100644
index 0000000..f38c296
--- /dev/null
+++ b/string/slice_hash.cc
@@ -0,0 +1,23 @@
+struct slice_hash {
+    using hash_type = pair<MLL<MDL1>, MLL<MDL2>>;
+    int n;
+    vector<MLL<MDL1>> pw1;
+    vector<MLL<MDL2>> pw2;
+    vector<MLL<MDL1>> hash1;
+    vector<MLL<MDL2>> hash2;
+    slice_hash(const string& s) : n(s.size()), pw1(n + 1), pw2(n + 1), hash1(n + 1), hash2(n + 1) {
+        constexpr int b = 31;
+        pw1[0] = 1, pw2[0] = 1;
+        for (int i = 1; i <= n; ++i) {
+            hash1[i] = hash1[i - 1] + s[i - 1] * pw1[i - 1];
+            hash2[i] = hash2[i - 1] + s[i - 1] * pw2[i - 1];
+            pw1[i] = pw1[i - 1] * b;
+            pw2[i] = pw2[i - 1] * b;
+        }
+    }
+
+    // query [l, r]
+    hash_type hash(int l, int r) {
+        return { (hash1[r + 1] - hash1[l]) / pw1[l], (hash2[r + 1] - hash2[l]) / pw2[l] };
+    }
+};