NQueens: done! backtracking: simple algorithm done! minConflicts: jus…

…t created!

.gitignore

@@ -0,0 +1,215 @@
+.idea/
+out/
+*.iml
+
+
+
+# Default ignored files
+/shelf/
+/workspace.xml
+# Datasource local storage ignored files
+/dataSources/
+/dataSources.local.xml
+# Editor-based HTTP Client requests
+/httpRequests/
+
+# Created by https://www.toptal.com/developers/gitignore/api/intellij,java,jetbrains
+# Edit at https://www.toptal.com/developers/gitignore?templates=intellij,java,jetbrains
+
+### Intellij ###
+# Covers JetBrains IDEs: IntelliJ, RubyMine, PhpStorm, AppCode, PyCharm, CLion, Android Studio, WebStorm and Rider
+# Reference: https://intellij-support.jetbrains.com/hc/en-us/articles/206544839
+
+# User-specific stuff
+.idea/**/workspace.xml
+.idea/**/tasks.xml
+.idea/**/usage.statistics.xml
+.idea/**/dictionaries
+.idea/**/shelf
+
+# Generated files
+.idea/**/contentModel.xml
+
+# Sensitive or high-churn files
+.idea/**/dataSources/
+.idea/**/dataSources.ids
+.idea/**/dataSources.local.xml
+.idea/**/sqlDataSources.xml
+.idea/**/dynamic.xml
+.idea/**/uiDesigner.xml
+.idea/**/dbnavigator.xml
+
+# Gradle
+.idea/**/gradle.xml
+.idea/**/libraries
+
+# Gradle and Maven with auto-import
+# When using Gradle or Maven with auto-import, you should exclude module files,
+# since they will be recreated, and may cause churn.  Uncomment if using
+# auto-import.
+# .idea/artifacts
+# .idea/compiler.xml
+# .idea/jarRepositories.xml
+# .idea/modules.xml
+# .idea/*.iml
+# .idea/modules
+# *.iml
+# *.ipr
+
+# CMake
+cmake-build-*/
+
+# Mongo Explorer plugin
+.idea/**/mongoSettings.xml
+
+# File-based project format
+*.iws
+
+# IntelliJ
+out/
+
+# mpeltonen/sbt-idea plugin
+.idea_modules/
+
+# JIRA plugin
+atlassian-ide-plugin.xml
+
+# Cursive Clojure plugin
+.idea/replstate.xml
+
+# Crashlytics plugin (for Android Studio and IntelliJ)
+com_crashlytics_export_strings.xml
+crashlytics.properties
+crashlytics-build.properties
+fabric.properties
+
+# Editor-based Rest Client
+.idea/httpRequests
+
+# Android studio 3.1+ serialized cache file
+.idea/caches/build_file_checksums.ser
+
+### Intellij Patch ###
+# Comment Reason: https://github.com/joeblau/gitignore.io/issues/186#issuecomment-215987721
+
+# *.iml
+# modules.xml
+# .idea/misc.xml
+# *.ipr
+
+# Sonarlint plugin
+# https://plugins.jetbrains.com/plugin/7973-sonarlint
+.idea/**/sonarlint/
+
+# SonarQube Plugin
+# https://plugins.jetbrains.com/plugin/7238-sonarqube-community-plugin
+.idea/**/sonarIssues.xml
+
+# Markdown Navigator plugin
+# https://plugins.jetbrains.com/plugin/7896-markdown-navigator-enhanced
+.idea/**/markdown-navigator.xml
+.idea/**/markdown-navigator-enh.xml
+.idea/**/markdown-navigator/
+
+# Cache file creation bug
+# See https://youtrack.jetbrains.com/issue/JBR-2257
+.idea/$CACHE_FILE$
+
+# CodeStream plugin
+# https://plugins.jetbrains.com/plugin/12206-codestream
+.idea/codestream.xml
+
+### Java ###
+# Compiled class file
+*.class
+
+# 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*
+
+### JetBrains ###
+# Covers JetBrains IDEs: IntelliJ, RubyMine, PhpStorm, AppCode, PyCharm, CLion, Android Studio, WebStorm and Rider
+# Reference: https://intellij-support.jetbrains.com/hc/en-us/articles/206544839
+
+# User-specific stuff
+
+# Generated files
+
+# Sensitive or high-churn files
+
+# Gradle
+
+# Gradle and Maven with auto-import
+# When using Gradle or Maven with auto-import, you should exclude module files,
+# since they will be recreated, and may cause churn.  Uncomment if using
+# auto-import.
+# .idea/artifacts
+# .idea/compiler.xml
+# .idea/jarRepositories.xml
+# .idea/modules.xml
+# .idea/*.iml
+# .idea/modules
+# *.iml
+# *.ipr
+
+# CMake
+
+# Mongo Explorer plugin
+
+# File-based project format
+
+# IntelliJ
+
+# mpeltonen/sbt-idea plugin
+
+# JIRA plugin
+
+# Cursive Clojure plugin
+
+# Crashlytics plugin (for Android Studio and IntelliJ)
+
+# Editor-based Rest Client
+
+# Android studio 3.1+ serialized cache file
+
+### JetBrains Patch ###
+# Comment Reason: https://github.com/joeblau/gitignore.io/issues/186#issuecomment-215987721
+
+# *.iml
+# modules.xml
+# .idea/misc.xml
+# *.ipr
+
+# Sonarlint plugin
+# https://plugins.jetbrains.com/plugin/7973-sonarlint
+
+# SonarQube Plugin
+# https://plugins.jetbrains.com/plugin/7238-sonarqube-community-plugin
+
+# Markdown Navigator plugin
+# https://plugins.jetbrains.com/plugin/7896-markdown-navigator-enhanced
+
+# Cache file creation bug
+# See https://youtrack.jetbrains.com/issue/JBR-2257
+
+# CodeStream plugin
+# https://plugins.jetbrains.com/plugin/12206-codestream
+
+# End of https://www.toptal.com/developers/gitignore/api/intellij,java,jetbrains

src/Backtracking.java

@@ -0,0 +1,67 @@
+import java.util.HashMap;
+import java.util.HashSet;
+
+public class Backtracking {
+    int variablesCount;
+
+    public Backtracking(int variablesCount) {
+        this.variablesCount = variablesCount;
+    }
+
+    public boolean FindResult(HashMap<Integer, Integer> assignments) {
+        if (assignments.size() == variablesCount)
+            return true;
+        HashSet<Integer> conflictedValues = new HashSet<>();
+        int variable = FindVariableWithMRV(assignments, conflictedValues);
+        for (int value = 0; conflictedValues.size() < variablesCount && value < variablesCount; value++)
+            if (!conflictedValues.contains(value)) {
+                assignments.put(variable, value);
+                if (FindResult(assignments))
+                    return true;
+                else {
+                    assignments.remove(variable);
+                }
+            }
+        if (assignments.size() > 220)
+            System.out.println(assignments.size());
+        return false;
+    }
+
+    /**
+     * find a variable with smallest domain of values( Minimum Remaining Values ).
+     *
+     * @param assignments      pairs of variables and their values.
+     * @param conflictedValues set of conflicted values for best variable.
+     * @return the variable with Minimum Remaining Values( the one with smallest domain ).
+     */
+    private int FindVariableWithMRV(HashMap<Integer, Integer> assignments, HashSet<Integer> conflictedValues) {
+        if (assignments.isEmpty()) {
+            return variablesCount / 2;
+        }
+        int maxConflictedValuesCount = 0;
+        int bestVariable = -1;
+        for (int i = 0; i < variablesCount; i++)
+            if (!assignments.containsKey(i)) {
+                HashSet<Integer> conflictedValuesOfCurrentVariable = new HashSet<>();
+                for (int variable : assignments.keySet()) {
+                    conflictedValuesOfCurrentVariable.add(assignments.get(variable));
+                    /**first line equation( y2-y1=m*(x2-x1) ): "x1=variable", "x2=i", "m=1", "y1=assignment.get(variable)" and "y2=value=?".*/
+                    int value = variable - i + assignments.get(variable);
+                    if (value < variablesCount && value >= 0)
+                        conflictedValuesOfCurrentVariable.add(value);
+                    /**second line equation: "x1=variable", "x2=i", "m=-1", "y1=assignment.get(variable)" and "y2=value=?".*/
+                    value = -variable + i + assignments.get(variable);
+                    if (value < variablesCount && value >= 0)
+                        conflictedValuesOfCurrentVariable.add(value);
+                }
+                if (conflictedValuesOfCurrentVariable.size() > maxConflictedValuesCount) {
+                    maxConflictedValuesCount = conflictedValuesOfCurrentVariable.size();
+                    bestVariable = i;
+                    conflictedValues.clear();
+                    conflictedValues.addAll(conflictedValuesOfCurrentVariable);
+                }
+            }
+        return bestVariable;
+    }
+
+}

src/MinConflicts.java

@@ -0,0 +1,2 @@
+public class MinConflicts {
+}

src/NQueens.java

@@ -0,0 +1,26 @@
+import java.util.HashMap;
+import java.util.Scanner;
+
+public class NQueens {
+    public static void main(String[] args) {
+        Scanner scanner = new Scanner(System.in);
+        System.out.println("how many queens?");
+        int n = scanner.nextInt();
+        Backtracking resultFinder = new Backtracking(n);
+//        MinConflicts resultFinder = new MinConflicts(n);
+        HashMap<Integer, Integer> result = new HashMap<>();
+        resultFinder.FindResult(result);
+        for (int key : result.keySet())
+            System.out.println(key + ": " + result.get(key));
+        scanner.next();
+        for (int i = 0; i < n; i++) {
+            for (int j = 0; j < n; j++) {
+                if (result.get(i) == j)
+                    System.out.print("|Q");
+                else
+                    System.out.print("|_");
+            }
+            System.out.println("|");
+        }
+    }
+}