change C->ch to fix name clash with KACTL's typedef complex<double> C;

Author: lrvideckis

library/math/n_choose_k/grow.hpp

@@ -5,9 +5,8 @@ struct comb {
 };
 vector<comb> t(2);
 void grow(int n) {
-  while (sz(t) <= n) {
-    ll i = sz(t),
-       inv = mod - (mod / i) * t[mod % i].inv % mod;
+  rep(i, sz(t), n + 1) {
+    ll inv = mod - (mod / i) * t[mod % i].inv % mod;
     t.push_back({inv, i * t[i - 1].fact % mod,
       inv * t[i - 1].inv_fact % mod});
   }

library/math/n_choose_k/lucas_theorem.hpp

@@ -7,6 +7,6 @@ ll lucas(ll n, ll k) {
   if (k < 0 || n < k) return 0;
   ll res = 1;
   for (; k && k < n && res; n /= mod, k /= mod)
-    res = res * C(n % mod, k % mod) % mod;
+    res = res * ch(n % mod, k % mod) % mod;
   return res;
 }

library/math/n_choose_k/n_choose_k.hpp

@@ -3,8 +3,7 @@
 //! n,k < mod
 //! @time O(1) amortized
 //! @space O(1) amortized
-// NOLINTNEXTLINE(readability-identifier-naming)
-ll C(int n, int k) {
+ll ch(int n, int k) {
   if (k < 0 || n < k) return 0;
   grow(n);
   return t[n].fact * t[k].inv_fact % mod *