CodeEval - Lowest Common Ancestor - Moderate

import java.io.BufferedReader;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.HashSet;
import java.util.LinkedList;
import java.util.StringTokenizer;

public class Main {

    public static void main(String[] args) throws FileNotFoundException, IOException {

        BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
        StringBuffer sb = new StringBuffer();
        String line;
        BinTree tree=setupTree();
        while ((line = in.readLine()) != null) {
            StringTokenizer st=new StringTokenizer(line);
            HashSet<Integer> hs=getPathHash(tree, Integer.parseInt(st.nextToken()));
            LinkedList<Integer> list=getPathList(tree, Integer.parseInt(st.nextToken()));
            boolean flag=false;
            while(!list.isEmpty()){
                int val=list.removeLast();
                if(hs.contains(val)){
                   sb.append(val);
                   flag=true;
                   break;
                }
            }
            if(flag)
                sb.append('\n');
        }
        System.out.print(sb);
    }
   
    static BinTree setupTree(){
        BinTree tree =new BinTree(30);
        BinTree temp=tree;
        temp.setLeft(8);
        temp.setRight(52);
        temp=temp.getLeft();
        temp.setLeft(3);
        temp.setRight(20);
        temp=temp.getRight();
        temp.setLeft(10);
        temp.setRight(29);
        return tree;
    }
   
    static  HashSet<Integer> getPathHash(BinTree b,int value){
         HashSet<Integer> hs=new HashSet<Integer>();
         BinTree temp=b;
         while(temp.getValue()!=value){
             hs.add(temp.getValue());
             if(temp.getValue()>value){
                 temp=temp.getLeft();
             }else{
                 temp=temp.getRight();
             }
         }
         hs.add(value);
         return hs;
    }
  
    static LinkedList<Integer> getPathList(BinTree b,int value){
         LinkedList<Integer> list=new LinkedList<Integer>();
         BinTree temp=b;
         while(temp.getValue()!=value){
             list.add(temp.getValue());
             if(temp.getValue()>value){
                 temp=temp.getLeft();
             }else{
                 temp=temp.getRight();
             }
         }
         list.add(value);
         return list;
    }
}

class BinTree{
   private BinTree right;
   private BinTree left;
   private int value;

    public BinTree(int x) {
        value=x;
        right=null;
        left=null;
    }

    public BinTree getLeft() {
        return left;
    }

    public void setLeft(int left) {
        this.left = new BinTree(left);
    }

    public BinTree getRight() {
        return right;
    }

    public void setRight(int right) {
        this.right = new BinTree(right);
    }

    public int getValue() {
        return value;
    }

    public void setValue(int value) {
        this.value = value;
    }
  
}

CodeEval - Find a Square - Moderate

import java.io.BufferedReader;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.Arrays;
import java.util.StringTokenizer;


public class Main {
    public static void main (String[] args) throws FileNotFoundException, IOException {

    BufferedReader in=new BufferedReader(new InputStreamReader(System.in));
    StringBuffer sb=new StringBuffer();
    String line;
    while ((line = in.readLine()) != null) {
        Point []points=new Point[4];
        StringTokenizer st=new StringTokenizer(line," ");
        for(int i=0;i<4;i++){
            points[i]=parsePoint(st.nextToken());
        }
        Point center=new Point(0,0);
        for(int i=0;i<4;i++){
            center.x+=points[i].x;
            center.y+=points[i].y;
        }
        center.x/=4;
        center.y/=4;
        boolean flag=true;
        double dist=eculDist(center, points[0]);
        for(int i=1;i<4;i++){
            double temp=eculDist(center, points[i]);
            if(temp!=dist){
                 sb.append(false).append("\n");
                 flag=false;
                 break;
            }
        }
        if(flag){
            int counter=0;
            for(int i=1;i<4;i++){
                if(dotProd(difPoint(points[0], center), difPoint(points[i], center))==0)
                        counter++;
            }
            if(counter==2){
                sb.append(true).append("\n");
            }
            else{
                sb.append(false).append("\n");
            }
        }
       
    }
    System.out.print(sb);
  }
   
    static double eculDist(Point p1,Point p2){
        return Math.sqrt(((p1.x-p2.x)*(p1.x-p2.x))+((p1.y-p2.y)*(p1.y-p2.y)));
    }
   
    static double dotProd(Point p1,Point p2){
        return p1.x*p2.x+p1.y*p2.y;
    }
   
    static Point difPoint(Point p1,Point p2){
        return new Point(p1.x-p2.x,p1.y-p2.y);
    }
   
    static Point parsePoint(String string){
        StringBuilder str=new StringBuilder(string);
        str.deleteCharAt(0);
        if(str.charAt(str.length()-1)==',')
            str.deleteCharAt(str.length()-1);
        str.deleteCharAt(str.length()-1);
        StringTokenizer st2=new StringTokenizer(str.toString(),",");
        return new Point(Integer.parseInt(st2.nextToken()),Integer.parseInt(st2.nextToken()));
    }
}

class Point{
    double x;
    double y;

    public Point(double x, double y) {
        this.x = x;
        this.y = y;
    }
   
   
}

CodeEval - Point in Circle - Moderate

import java.io.BufferedReader;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.StringTokenizer;


public class Main {
    public static void main (String[] args) throws FileNotFoundException, IOException {

    BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
    StringBuffer sb=new StringBuffer();
    String line;
    while ((line = in.readLine()) != null) {
        StringTokenizer st=new StringTokenizer(line,";");
        StringBuilder str=new StringBuilder(st.nextToken());
        str.delete(0, 9);
        str.deleteCharAt(str.length()-1);
        StringTokenizer st2=new StringTokenizer(str.toString(),",");
        double centerX=Double.parseDouble(st2.nextToken());
        double centerY=Double.parseDouble(st2.nextToken().trim());
       
        str=new StringBuilder(st.nextToken());
        str.delete(0, 9);
        double radius=Double.parseDouble(str.toString());
       
        str=new StringBuilder(st.nextToken());
        str.delete(0, 9);
        str.deleteCharAt(str.length()-1);
        st2=new StringTokenizer(str.toString(),",");
        double pX=Double.parseDouble(st2.nextToken());
        double pY=Double.parseDouble(st2.nextToken().trim());
        sb.append(!(eculDist(pX, pY, centerX, centerY)>radius)).append("\n");
    }
    System.out.print(sb);
  }
   
    static double eculDist(double x1,double y1,double x2,double y2){
        return Math.sqrt(((x1-x2)*(x1-x2))+((y1-y2)*(y1-y2)));
    }
}

CodeEval - Sudoku - Moderate

import java.io.BufferedReader;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.StringTokenizer;

public class Main {

    public static void main(String[] args) throws FileNotFoundException, IOException {

        BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
        StringBuffer sb = new StringBuffer();
        String line;
        while ((line = in.readLine()) != null) {
            StringTokenizer st=new StringTokenizer(line,";");
            int n=Integer.parseInt(st.nextToken());
            int arr[][]=new int[n][n];
            StringTokenizer valz=new StringTokenizer(st.nextToken(),",");
            for(int i=0;i<n;i++){
                for(int j=0;j<n;j++){
                    arr[i][j]=Integer.parseInt(valz.nextToken());
                }
            }
            if(checkSoduku(arr)){
                sb.append("True\n");
            }else{
                sb.append("False\n");
            }
        }
        System.out.print(sb);
    }
   
     static boolean checkSoduku(int[][]arr){
         int n=arr.length;
         for(int i=0;i<n;i++){
             boolean[] valz=new boolean[n+1];
             for(int j=0;j<n;j++){
                 if(arr[i][j]>n){
                     return false;
                 }
                 valz[arr[i][j]]=true;
             }
             for(int j=1;j<valz.length;j++){
                 if(!valz[j]){
                     return false;
                 }
             }
         }
         for(int i=0;i<n;i++){
             boolean[] valz=new boolean[n+1];
             for(int j=0;j<n;j++){
                 if(arr[j][i]>n){
                     return false;
                 }
                 valz[arr[j][i]]=true;
             }
             for(int j=1;j<valz.length;j++){
                 if(!valz[j]){
                     return false;
                 }
             }
         }
         int sqX=(int) Math.sqrt(n);
         for(int i=0;i<sqX*sqX;i+=sqX){
             for(int j=0;j<sqX*sqX;j+=sqX){
                 boolean[] valz=new boolean[n+1];
                 for(int z=i;z<i+sqX;z++){
                     for(int k=j;k<j+sqX;k++){
                        valz[arr[z][k]]=true;
                     }
                 }
                 for(int z=1;z<valz.length;z++){
                    if(!valz[z]){
                         return false;
                    }
                 }
             }
         }
         return true;
     }
}