fix some bug

zimpha · zimpha · commit 173adc8b3c46 · 2016-09-07T23:12:31.000+08:00
diff --git a/mathematics/basic.hpp b/mathematics/basic.hpp
@@ -55,7 +55,7 @@ void exgcd(LL a, LL b, LL &g, LL &x, LL &y) {
 LL mod_inv(LL a, LL m) {
   LL d, x, y;
   exgcd(a, m, d, x, y);
-  return d == 1 ? (x % + m) % m : -1;
+  return d == 1 ? (x % m + m) % m : -1;
 }
 
 //ax + by = c,x >= 0, x is minimum
diff --git a/mathematics/congruence-equations.cc b/mathematics/congruence-equations.cc
@@ -1,14 +1,14 @@
 #include "basic.hpp"
 
 // 中国剩余定理， 要求m[i]互质
-// x = a[i] (mod m[i]) (0 <= i < n)
+// x = c[i] (mod m[i]) (0 <= i < n)
 LL crt(int n, LL *c, LL *m) {
   LL M = 1, ans = 0;
   for (int i = 0; i < n; ++i) M *= m[i];
   for (int i = 0; i < n; ++i) {
     LL x, y, g, tm = M / m[i];
     exgcd(tm, m[i], g, x, y);
-    ans = (ans + tm * x * a[i] % M) % M;
+    ans = (ans + tm * x * c[i] % M) % M;
   }
   return (ans + M) % M;
 }
diff --git a/mathematics/prime.cc b/mathematics/prime.cc
@@ -7,7 +7,7 @@ struct Primality {
     if (n <= 1) return false;
     if (n <= 3) return true;
     if (~n & 1) return false;
-    const int u[] = {2,325,9375,28178,450775,9780504,1795265022,0};
+    const int u[] = {2,3,5,7,325,9375,28178,450775,9780504,1795265022,0};
     LL e = n - 1, a, c = 0; // 原理：http://miller-rabin.appspot.com/
     while (~e & 1) e >>= 1, ++c;
     for (int i = 0; u[i]; ++i) {
