add c++ implementation

Author: ice1000

jni/global/templates.hpp

@@ -33,15 +33,22 @@ using algo4j_util::swap;
 namespace algo4j_math {
 
 template<typename T>
-auto fast_plus(T a, T b, T _) -> T {
+auto fast_plus(T a, T b, T m) -> T {
+auto s = a + b;
+if (s >= a and s >= b) return s % m;
+if (a >= m and a > m - b) return fast_plus(a - m, b, m);
+if (b >= m and b > m - a) return fast_plus(a, b - m, m);
+return s;
+}
+
+template<typename T>
+auto fast_mul(T a, T b, T _) -> T {
 T ret = 0;
 while (b) {
 if (b bitand 1)
-ret = (ret + a) % _;
+ret = fast_plus(ret, a, _);
 b >>= 1;
-//a <<= 1;
-//a %= _;
-a = (a << 1) % _;
+a = fast_plus(a, a, _);
 }
 return ret;
 }
@@ -51,9 +58,9 @@ namespace algo4j_math {
 T ret = 1;
 while (b) {
 if (b bitand 1)
-ret = fast_plus(ret, a, m);
+ret = fast_mul(ret, a, m);
 b >>= 1;
-a = fast_plus(a, a, m);
+a = fast_mul(a, a, m);
 }
 return ret;
 }

jni/math/MathUtils.cpp

@@ -70,6 +70,15 @@ JNIEXPORT auto JNICALL Java_org_algo4j_math_MathUtils_fastPlus(
 return fast_plus(a, b, m);
 }
 
+JNIEXPORT auto JNICALL Java_org_algo4j_math_MathUtils_fastMul(
+JNIEnv *env,
+jclass jc,
+jlong a,
+jlong b,
+jlong m) -> jlong {
+return fast_mul(a, b, m);
+}
+
 JNIEXPORT auto JNICALL Java_org_algo4j_math_MathUtils_fastPower(
 JNIEnv *env,
 jclass jc,

jni/math/MathUtils.h

@@ -74,6 +74,31 @@ JNIEXPORT auto JNICALL Java_org_algo4j_math_MathUtils_sqrt(
 jdouble
 ) -> jdouble;
 
+/**
+ * Class: org_algo4j_math_MathUtils
+ * Method: fastMul
+ * Signature: (JJJ)J
+ */
+JNIEXPORT auto JNICALL Java_org_algo4j_math_MathUtils_fastMul(
+JNIEnv *,
+jclass,
+jlong,
+jlong,
+jlong
+) -> jlong;
+
+/**
+ * Class: org_algo4j_math_MathUtils
+ * Method: fastPlus
+ * Signature: (JJJ)J
+ */
+JNIEXPORT auto JNICALL Java_org_algo4j_math_MathUtils_fastPlus(
+JNIEnv *,
+jclass,
+jlong,
+jlong,
+jlong
+) -> jlong;
 /**
  * Class: org_algo4j_math_MathUtils
  * Method: fastPlus

src/test/kotlin/org/algo4j/math/MathUtilsTest.kt

@@ -106,7 +106,7 @@ class MathUtilsTest {
 assertEquals(12, fastPower(2, 9, 100))
 assertEquals(4, fastPower(2, 10, 10))
 assertEquals(289, fastMul(233, 233, 1000))
-assertEquals(3, fastPlus(233, 233, 10))
+assertEquals(6, fastPlus(233, 233, 10))
 }
 
 /**