Fixed the bug of power of zero.

Author: a1fredbao

src/alfred/math/mod-int.hpp

@@ -46,7 +46,6 @@ class ModInt {
         if (n < 0) {
             n = (-n) % (M - 1) * (M - 2);
         }
-        n %= (M - 1);
         while (n) {
             if (n & 1) res *= x;
             x *= x;

src/alfred/math/utils.hpp

@@ -31,6 +31,11 @@ inline T isqrt(T x) {
     return res;
 }
 
+template <class T, class V>
+inline bool in_range(V v, T l, T r) {
+    return l <= v && v <= r;
+}
+
 // Given in integer n. Returns (primes, minp)
 std::pair<std::vector<int>, std::vector<int>> euler_sieve(int n) {
     std::vector<int> primes, minp(n + 1);