Optimize and make Modint safer

Author: Matistjati

content/number-theory/ModularArithmetic.h

@@ -1,5 +1,5 @@
 /**
- * Author: Lukas Polacek
+ * Author: Lukas Polacek, Joshua Andersson
  * Date: 2009-09-28
  * License: CC0
  * Source: folklore
@@ -13,14 +13,15 @@
 const ll mod = 17; // change to something else
 struct Mod {
 	ll x;
-	Mod(ll xx) : x(xx) {}
-	Mod operator+(Mod b) { return Mod((x + b.x) % mod); }
-	Mod operator-(Mod b) { return Mod((x - b.x + mod) % mod); }
-	Mod operator*(Mod b) { return Mod((x * b.x) % mod); }
+	Mod(ll y) : Mod(y%mod+mod,0){}
+	Mod(ll y,int) : x(y<mod?y:y-mod){}
+	Mod operator+(Mod b) { return {x + b.x,0}; }
+	Mod operator-(Mod b) { return {x - b.x + mod,0}; }
+	Mod operator*(Mod b) { return {x * b.x % mod,0}; }
 	Mod operator/(Mod b) { return *this * invert(b); }
 	Mod invert(Mod a) {
-		ll x, y, g = euclid(a.x, mod, x, y);
-		assert(g == 1); return Mod((x + mod) % mod);
+		ll x, y, g = euclid(a.x,mod,x,y);
+		assert(g == 1); return x;
 	}
 	Mod operator^(ll e) {
 		if (!e) return Mod(1);