add rolling hash snippet

lua/custom/snippets/edhliicpp.lua

@@ -216,4 +216,29 @@ ls.add_snippets('cpp', {
       '};',
     }
   ),
+  s('rollinghash', {
+    t {
+      'struct RollingHash {',
+      '  using ll = long long;',
+      '  ll base, mod;',
+      '  vector<ll> power;',
+      '  vector<ll> prefix_hash;',
+      '  RollingHash(const string &s, ll base, ll mod) : base(base), mod(mod) {',
+      '    int n = s.size();',
+      '    power.resize(n + 1, 1);',
+      '    prefix_hash.resize(n + 1, 0);',
+      '    for (int i = 0; i < n; ++i) {',
+      '      power[i + 1] = (__int128)power[i] * base % mod;',
+      '      prefix_hash[i + 1] = ((__int128)prefix_hash[i] * base + s[i]) % mod;',
+      '    }',
+      '  }',
+      '  ll get_hash(int l, int r) {',
+      '    ll hash_r = prefix_hash[r + 1];',
+      '    ll hash_l = (__int128)prefix_hash[l] * power[r - l + 1] % mod;',
+      '    ll res = (hash_r - hash_l + mod) % mod;',
+      '    return res;',
+      '  }',
+      '};',
+    },
+  }),
 })