feat: add modular inv

.gitignore

@@ -1,54 +1,11 @@
-# ---> Java
+out/
-# Compiled class file
+build
-*.class
+classes
-
-# Log file
-*.log
-
-# BlueJ files
-*.ctxt
-
-# Mobile Tools for Java (J2ME)
-.mtj.tmp/
-
-# Package Files #
-*.jar
-*.war
-*.nar
-*.ear
-*.zip
-*.tar.gz
-*.rar
-
-# virtual machine crash logs, see http://www.java.com/en/download/help/error_hotspot.xml
-hs_err_pid*
-replay_pid*
-
-# ---> macOS
-# General
 .DS_Store
-.AppleDouble
+.gradle
-.LSOverride
+.classpath
-
+.project
-# Icon must end with two \r
+.settings
-Icon
+*.iml
-
+*.ipr
-
+*.iws
-# Thumbnails
-._*
-
-# Files that might appear in the root of a volume
-.DocumentRevisions-V100
-.fseventsd
-.Spotlight-V100
-.TemporaryItems
-.Trashes
-.VolumeIcon.icns
-.com.apple.timemachine.donotpresent
-
-# Directories potentially created on remote AFP share
-.AppleDB
-.AppleDesktop
-Network Trash Folder
-Temporary Items
-.apdisk

build.gradle

@@ -0,0 +1,100 @@
+apply plugin: 'java'
+apply plugin: 'eclipse'
+apply plugin: 'idea'
+
+def JsonSlurper = Class.forName('groovy.json.JsonSlurper');
+def buildJSON = JsonSlurper.newInstance().parseText(new File("build.json").text)
+
+if (buildJSON.application) { apply plugin: 'application' }
+
+def baseProjectName = buildJSON?.project?.name ?: '__project_name__';
+def shellCommandName = baseProjectName
+def eclipseProjectName = baseProjectName
+def eclipseProjectComment = buildJSON?.project?.comment ?: '__project_name_comment__'
+def jarManifestMainClass = buildJSON?.project?.main ?: 'SampleMain'
+
+if (buildJSON.application) { mainClassName = jarManifestMainClass }
+archivesBaseName = buildJSON?.project?.archiveName ?: baseProjectName
+sourceCompatibility = 1.8
+targetCompatibility = 1.8
+
+def addRepo = new File(System.getProperty("user.home"), ".build_add.repo")
+
+repositories {
+  mavenLocal()
+  // mavenCentral()
+  maven() { url 'https://maven.aliyun.com/repository/central' }
+  if (addRepo.exists()) { maven() { url addRepo.text.trim() } }
+}
+
+tasks.withType(JavaCompile) {
+  options.encoding = "UTF-8"  
+}
+
+// '-x test' skip unit test
+defaultTasks 'packjar'
+
+task packjarsrc << {
+  ant.jar(destfile: "${baseProjectName}-sources.jar") {
+    fileset(dir: 'src/main/java', includes: '**/*.java')
+  }
+}
+packjarsrc.dependsOn build
+
+task packjar << {
+  def packtempclasses = "packtempclasses"
+  def libs = ant.path {
+     fileset(dir: 'build/libs', includes: '*.jar')
+  }
+  libs.list().each {
+    ant.unzip(dest: packtempclasses, src: it)
+  }
+  new File(packtempclasses + "/jar-version-build.txt").write(new Date().format("yyyyMMdd"), "UTF-8")
+  ant.jar(destfile: "${baseProjectName}.jar") {
+    fileset(dir: packtempclasses, includes: '**/*.*')
+  }
+  ant.delete(dir: packtempclasses)
+}
+packjar.dependsOn packjarsrc
+
+dependencies {
+    compile files(fileTree(dir: 'lib', includes: ['*.jar'], excludes: ['*-sources.jar', '*-javadoc.jar']))
+
+    if (buildJSON.repo != null && buildJSON.repo.dependencies != null) {
+        buildJSON.repo.dependencies.each {
+            compile("${it}")
+        }
+    }
+    if (buildJSON.repo != null && buildJSON.repo.testDependencies != null) {
+        buildJSON.repo.testDependencies.each {
+            testCompile("${it}")
+        }
+    }
+}
+
+eclipse {
+  project {
+    name = eclipseProjectName
+    comment = eclipseProjectComment
+  }
+  classpath {
+    defaultOutputDir = file('classes')
+    downloadSources = true
+    file {
+      whenMerged { classpath ->
+        classpath.entries.findAll { it.kind=='lib' }.each {
+          if ((it.path != null) && (it.sourcePath == null) && file(it.path.replace(".jar", "-sources.jar")).exists()) { 
+            it.sourcePath = getFileReferenceFactory().fromPath(it.path.replace(".jar", "-sources.jar"))
+          }
+        }
+      }
+    }
+  }
+}
+
+eclipseJdt << {
+  File f = file('.settings/org.eclipse.core.resources.prefs')
+  f.write('eclipse.preferences.version=1\n')
+  f.append('encoding/<project>=utf-8')
+}
+

build.json

@@ -0,0 +1,21 @@
+{
+    "project": {
+        "name": "math",
+        "main": "SampleMain",
+        "archiveName": "math"
+    },
+    "application": false,
+    "java": "1.8",
+    "builder": {
+        "name": "gradle",
+        "version": "3.1"
+    },
+    "repo": {
+        "dependencies": [
+            "me.hatter:commons:3.0"
+        ],
+        "testDependencies": [
+            "junit:junit:4.12"
+        ]
+    }
+}

src/main/java/me/hatter/math/ModularInv.java

@@ -0,0 +1,63 @@
+package me.hatter.math;
+
+import java.math.BigInteger;
+import java.util.Arrays;
+
+// https://zhuanlan.zhihu.com/p/426499159
+// def modular_inv(a, p):
+//    x, y, m = 1, 0, p
+//    while a > 1:
+//        q = a // m
+//        t = m
+//
+//        m = np.mod(a, m)
+//        a = t
+//        t = y
+//
+//        y, x = x - np.int64(q) * np.int64(y), t
+//
+//        if x < 0:
+//            x = np.mod(x, p)
+//    return np.mod(x, p)
+public class ModularInv {
+
+    public static void main(String[] args) {
+        for (long i = 1; i < 10000; i++) {
+            for (long j = 1; j < 10000; j++) {
+                BigInteger a = BigInteger.valueOf(i);
+                BigInteger p = BigInteger.valueOf(j);
+                if (!a.gcd(p).equals(BigInteger.ONE)) {
+                    continue;
+                }
+                BigInteger x = a.modInverse(p);
+                BigInteger y = modularInv(a, p);
+                System.out.println(Arrays.asList(a, p, a.modInverse(p), modularInv(a, p)));
+                if (!y.equals(x)) {
+                    throw new RuntimeException();
+                }
+            }
+        }
+    }
+
+    public static BigInteger modularInv(BigInteger a, BigInteger p) {
+        BigInteger x = BigInteger.ONE;
+        BigInteger y = BigInteger.ZERO;
+        BigInteger m = p;
+        while (a.compareTo(BigInteger.ONE) > 0) {
+            BigInteger q = a.divide(m);
+            BigInteger t = m;
+
+            m = a.mod(m);
+            a = t;
+            t = y;
+
+            y = x.subtract(q.multiply(y));
+            x = t;
+
+            if (x.compareTo(BigInteger.ZERO) < 0) {
+                x = x.mod(p);
+            }
+        }
+        return x.mod(p);
+    }
+}