nqueens

refactor diagonal checking

add maven jdk compiler version

Author: jbequinn

Algorithms/pom.xml

@@ -7,11 +7,11 @@
   <version>1.0-SNAPSHOT</version>
   <name>Algorithms</name>
   <url>http://maven.apache.org</url>
-  
+
 <properties>
   <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
 </properties>
-  
+
   <dependencies>
     <dependency>
       <groupId>junit</groupId>
@@ -20,4 +20,20 @@
       <scope>test</scope>
     </dependency>
   </dependencies>
+
+
+<build>
+    <plugins>
+        <plugin>
+            <groupId>org.apache.maven.plugins</groupId>
+            <artifactId>maven-compiler-plugin</artifactId>
+            <version>2.3.2</version>
+            <configuration>
+                <source>1.6</source>
+                <target>1.6</target>
+            </configuration>
+        </plugin>
+    </plugins>
+</build>
+
 </project>

NQueens-backtrack/pom.xml

@@ -7,24 +7,39 @@
   <version>1.0-SNAPSHOT</version>
   <name>NQueens-backtrack</name>
   <url>http://maven.apache.org</url>
-  
+
   <properties>
       <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
   </properties>
-  
+
   <dependencies>
     <dependency>
       <groupId>junit</groupId>
       <artifactId>junit</artifactId>
       <version>4.11</version>
       <scope>test</scope>
     </dependency>
-    
+
     <dependency>
       <groupId>com.dodecaedro</groupId>
       <artifactId>Algorithms</artifactId>
       <version>1.0-SNAPSHOT</version>
     </dependency>
-        
+
   </dependencies>
+
+<build>
+    <plugins>
+        <plugin>
+            <groupId>org.apache.maven.plugins</groupId>
+            <artifactId>maven-compiler-plugin</artifactId>
+            <version>2.3.2</version>
+            <configuration>
+                <source>1.6</source>
+                <target>1.6</target>
+            </configuration>
+        </plugin>
+    </plugins>
+</build>
+
 </project>

NQueens-backtrack/src/main/java/com/dodecaedro/backtrack/nqueens/Queen.java

@@ -26,33 +26,20 @@ public boolean isInSameYColumn(Queen otherQueen) {
 	}
 
 	public boolean isInSameDiagonal(Queen otherQueen) {
-		// first diagonal \
+		// based on y = x + a
+		// if they're on the same diagonal, y - x = a
+		
+		// first diagonal /
 		if ((this.positionX-this.positionY)==(otherQueen.positionX-otherQueen.positionY)) {
 			return true;
 		}
-		// now test /
-		// down and left
-		int posX = this.positionX;
-		int posY = this.positionY;
-		while(posX >= 0 && posY <= NQueensNode.SIZE) {
-			posX--;
-			posY++;
-			if (posX == otherQueen.positionX && posY == otherQueen.positionY) {
-				return true;
-			}			
-		}
-		
-        // up and right
-		posX = this.positionX;
-		posY = this.positionY;
-		while(posX <= NQueensNode.SIZE && posX <= NQueensNode.SIZE) {
-			posX++;
-			posY--;
-			if (posX == otherQueen.positionX && posY == otherQueen.positionY) {
-				return true;
-			}			
-		}
 
+		// in this case, it's y = -x +a
+		// diagonal \
+		if ((this.positionX+this.positionY)==(otherQueen.positionX+otherQueen.positionY)) {
+			return true;
+		}		
+			
 		// not in any same diagonal
 		return false;
 	}