Longest Common Prefix

function to find the longest common prefix string amongst an array of strings. If there is no common prefix, return an empty string "".

       
       
       

class Solution {
   public static void main(String[] args) {
    System.out.println("Should be (fl). ="+new Solution().longestCommonPrefix(new String[]{"flower","flow","flight"}));
    System.out.println("Should be (""). ="+new Solution().longestCommonPrefix(new String[]{"box","wow","cat"})); 
  }
    
    public String longestCommonPrefix(String[] strs) {
        String firstString = strs[0];
        String commonPrefix="";
      boolean common=true;
        for(int j=0; j

Roman to decimal conversion

       
       
class Solution {
   public static void main(String[] args) {
    System.out.println("Should be (3). ="+new Solution().romanToInt("III"));
     
      System.out.println("Should be (58). ="+new Solution().romanToInt("LVIII"));
      System.out.println("Should be (1994). ="+new Solution().romanToInt("MCMXCIV"));
  }
    public int romanToInt(String s) {
        Map romanValues = new HashMap();
        romanValues.put("I", "1");
        romanValues.put("V", "5");
        romanValues.put("X", "10");
        romanValues.put("L", "50");
        romanValues.put("C", "100");
        romanValues.put("D", "500");
        romanValues.put("M", "1000");
        String romanNum = s;
        int intValue=0;
        int prevValue=0;
        for(int i=0; i< s.length(); i++){
            String firstChar = romanNum.substring(0,1);
            if(firstChar==null)
                continue;
           System.out.println("firstChar= "+firstChar);
            
            int romanIntValue= Integer.valueOf((String)romanValues.get(firstChar));
           System.out.println("romanIntValue= "+romanIntValue);
          if(romanIntValue > prevValue){
            romanIntValue -=prevValue;
            intValue -=prevValue;
          }
            
           prevValue=romanIntValue;
            intValue +=romanIntValue;
           System.out.println("intValue= "+intValue);
          
          romanNum = romanNum.substring(1, romanNum.length());
           System.out.println("romanNum= "+romanNum);
        }
        return intValue;
    }
}
       

Polindrome

 Given an integer x, return true if x is palindrome integer.

An integer is a palindrome when it reads the same backward as forward.

• For example, 121 is a palindrome while 123 is not.

class Polindrome {

    public boolean isPalindrome(int x) {

        int given =x;

        int reverse=0;

        while(given >0){

            reverse = 10*reverse +given%10;

            given = given/10;

        }

        if(reverse == x)

        return true;

        return false;

    }

}

This one only goes through half the elements

class Palindrome {

    public boolean isPalindrome(int x) {

// negative numbers are not a palindrome

//any number with zero in units. but not Zero by itself 

     if(x<0  || (x % 10 == 0 && x != 0) )

         return false;

    int numDigits = String.valueOf(x).length();

        int half = numDigits/2;

            int rev=0;

            int given = x;

        for(int i=0;i<half;i++){

            rev = 10*rev+given%10;

            given=given/10;

        }

        if(numDigits%2 != 0)

            given = given/10;

            if(rev==given)

                return true;

       return false;

    }

}