diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..6b468b6
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1 @@
+*.class
diff --git a/leetcode/1-Easy-Two-Sum/Solution.java b/leetcode/1-Easy-Two-Sum/Solution.java
new file mode 100644
index 0000000..6b17238
--- /dev/null
+++ b/leetcode/1-Easy-Two-Sum/Solution.java
@@ -0,0 +1,29 @@
+import java.util.*;
+
+class Solution {
+    public static int[] twoSum(int[] nums, int target) 
+    {
+        Map<Integer,Integer> m = new HashMap<>();
+        
+            for(int i = 0; i < nums.length; i++){
+                 m.put(nums[i],i);
+            }
+            System.out.println(m.size());
+
+            for(int i = 0; i < nums.length; i++)
+            {
+                if(m.containsValue(target - nums[i] )&& m.get(target - nums[i]) != i)
+                {
+                    int n[] = new int[]{ m.get(target - nums[i]), i};
+                    return n;
+                }
+            }
+        
+         throw new IllegalArgumentException("No two sum solution");
+    }
+    public static void main(String[] args) {
+        int nums[] = new int[]{3,3};
+        System.out.println(twoSum(nums, 6));
+
+    }
+}
\ No newline at end of file
diff --git a/leetcode/12-Medium-Integer-To-Roman/Solution.java b/leetcode/12-Medium-Integer-To-Roman/Solution.java
new file mode 100644
index 0000000..6d964d0
--- /dev/null
+++ b/leetcode/12-Medium-Integer-To-Roman/Solution.java
@@ -0,0 +1,21 @@
+class Solution {
+    public static String intToRoman(int num) {
+        StringBuilder sb = new StringBuilder();
+        int values[] = {1000,900,500,400,100,90,50,40,10,9,5,4,1};
+        String syms[] = {"M","CM","D","CD","C","XC","L","XL","X","IX","V","IV","I"}; 
+        int pnt = 0;
+        while (num > 0) {
+            if (num >= values[pnt]) {
+                sb.append(syms[pnt]);
+                num = num - values[pnt];
+            } else {
+                pnt++;
+            }
+        }
+        return sb.toString();
+    }
+    public static void main(String[] args)
+     {
+        System.out.println(intToRoman(1050));
+    }
+}
\ No newline at end of file
diff --git a/leetcode/13-Easy-Roman-To-Integer/Solution.java b/leetcode/13-Easy-Roman-To-Integer/Solution.java
new file mode 100644
index 0000000..d22a4b9
--- /dev/null
+++ b/leetcode/13-Easy-Roman-To-Integer/Solution.java
@@ -0,0 +1,38 @@
+import java.util.*;
+
+class solution
+{
+    public  static int romanToInt(String s) 
+    {
+           int sum = 0;
+            char ch1='0', ch2='0';
+            for(int i=0;i<s.length();i++){
+                ch1 = s.charAt(i);
+                if(i+1<s.length())  ch2 = s.charAt(i+1);
+                if(ch1=='I'&& ch2=='V') {sum+=4;i++;continue;}
+                if(ch1=='X'&& ch2=='L') {sum+=40;i++;continue;}
+                if(ch1=='C'&& ch2=='D') {sum+=400;i++;continue;}
+                if(ch1=='I'&& ch2=='X') {sum+=9;i++;continue;}
+                if(ch1=='X'&& ch2=='C') {sum+=90;i++;continue;}
+                if(ch1=='C'&& ch2=='M') {sum+=900;i++;continue;}
+                
+                switch(ch1){
+                    case 'I': sum += 1;break;
+                    case 'V': sum += 5;break;
+                    case 'X': sum += 10;break;
+                    case 'L': sum += 50;break;
+                    case 'C': sum += 100;break;
+                    case 'D': sum += 500;break;
+                    case 'M': sum += 1000;break;
+                }
+            }
+            return sum;   
+            
+    }
+    public static void main(String[] args)
+   {
+       String s =  "LVIII";
+       System.out.println(romanToInt(s));
+        
+    }
+}
\ No newline at end of file
diff --git a/leetcode/14-Easy-Longest-Common-Prefix/Solution.java b/leetcode/14-Easy-Longest-Common-Prefix/Solution.java
new file mode 100644
index 0000000..ebc8f48
--- /dev/null
+++ b/leetcode/14-Easy-Longest-Common-Prefix/Solution.java
@@ -0,0 +1,38 @@
+import java.util.*;
+class Solution {
+    public static String longestCommonPrefix(String[] strs) 
+    {
+         if (strs == null || strs.length == 0) return "";
+         if(strs.length == 1) return strs[0];
+        int prefix = 0 ;
+        boolean flag = true ;
+        while(flag && prefix < strs[0].length())
+        {
+            char ch = strs[0].charAt(prefix);
+            for(int i = 1; i < strs.length ;i++)
+            {
+                  if( prefix < strs[i].length())
+                {
+                    if(ch == strs[i].charAt(prefix))
+                    {
+                        flag = true;
+                    }
+                 else{
+                     if(prefix == 0)
+                     {
+                         return "";
+                     }
+                   flag = false;                  
+                 }
+                }
+            }
+            prefix++;  
+        }
+        return strs[0].length() == 0 ? "" : prefix == 1 ? strs[0].substring(0, 1) :strs[0].substring(0, prefix - 1);
+       
+    }   
+    public static void main(String[] args) {
+        String[] strs = new String[]{"flower","flow","flight"};
+        System.out.println(longestCommonPrefix(strs));
+    }
+}
\ No newline at end of file
diff --git a/leetcode/2-Medium-Add-Two-Numbers/Solution.java b/leetcode/2-Medium-Add-Two-Numbers/Solution.java
new file mode 100644
index 0000000..f785320
--- /dev/null
+++ b/leetcode/2-Medium-Add-Two-Numbers/Solution.java
@@ -0,0 +1,96 @@
+import java.util.*;
+
+public class Solution 
+{
+    public ListNode addTwoNumbers(ListNode l1, ListNode l2) 
+    {  
+     return adder(l1,l2,0);   
+    }
+    public ListNode adder(ListNode l1, ListNode l2, int carry) 
+    {  
+       if (l1 == null && l2 == null ) 
+       {
+            if (carry == 0) 
+                return null;
+            else 
+                return new ListNode(1);
+        }
+        int sum = (l1 == null ? 0: l1.val) + (l2 == null ? 0: l2.val) + carry;
+        ListNode result = new ListNode(sum % 10);
+        result.next = adder((l1==null ? null : l1.next),(l2==null ? null : l2.next),sum/10);
+            
+        return result;
+        
+    }
+
+    /// testing
+    public static void main(String[] args) 
+    {
+        int num1 = 342;
+        int num2 = 465;
+        int n = num1 % 10;             // n = 2
+        ListNode l1 = new ListNode(n);
+        ListNode node1 = l1;
+        num1 = num1 /10;
+        while(num1 > 0)
+        {
+            n = num1 % 10;
+            node1.next = new ListNode(n);
+            num1 = num1 / 10;
+            node1 = node1.next;
+        }
+        n = num2 % 10;            // n = 5
+        ListNode l2= new ListNode(n);
+        ListNode node2 = l2;
+        num2 = num2 /10;
+        while(num2 > 0)
+        {
+            n = num2 % 10;
+            node2.next = new ListNode(n);
+            num2 = num2 / 10;
+            node2 = node2.next;
+        }
+        Solution s = new Solution();
+
+        // calling function  addTwoNumber , it will return result linkedlist ...........
+        ListNode result = s.addTwoNumbers(l1, l2);
+
+        /// printing input linkedlist 1...........
+        System.out.print("Input :  ");
+        while(l1.next!= null)
+        {
+            System.out.print((l1 == null ? "": l1.val+"->"));
+            l1 = l1.next;
+           
+        }
+        System.out.print(l1 != null ? l1.val : "");
+
+        /// printing input linkedlist 2.............
+
+        System.out.print(" + ");
+
+        while(l2.next != null)
+        {
+            System.out.print((l2 == null ? "": l2.val+"->"));
+            l2 = l2.next;
+        }
+        System.out.println(l2 != null ? l2.val : "");
+
+        //printing result linkedlist............
+        System.out.print("Output : ");
+        while(result.next != null)
+        {
+            System.out.print(result.val +"->");
+            result = result.next;
+        }
+        System.out.println(result != null ? result.val : "");
+        
+    }
+    
+}
+class ListNode {
+    int val;
+    ListNode next;
+    ListNode(int x) { val = x; }
+    }
+
diff --git a/leetcode/26-Easy-Remove-Duplicates-From-Sorted-Array/Solution.java b/leetcode/26-Easy-Remove-Duplicates-From-Sorted-Array/Solution.java
new file mode 100644
index 0000000..9eca1b5
--- /dev/null
+++ b/leetcode/26-Easy-Remove-Duplicates-From-Sorted-Array/Solution.java
@@ -0,0 +1,40 @@
+import java.util.*;
+
+class Solution {
+  /*  public static int removeDuplicates(int[] nums)
+    { 
+         LinkedHashSet<Integer> hs = new LinkedHashSet<>();
+        int j = 0;
+        for(int i = 0 ; i < nums.length; i++)
+        {
+           if( hs.add(nums[i]))
+           {
+              nums[j] = nums[i]; 
+               j++;
+           }
+           
+        }
+        return hs.size();
+        
+    }
+    */
+    public static int removeDuplicates(int[] nums)
+    {
+        int j = 0;
+        for(int i = 1 ; i< nums.length; i++)
+        {
+            if(nums[j] != nums[i])
+            {
+                 j++;
+             nums[j] = nums[i];
+               
+            }
+        }
+        return j + 1;
+        
+    }
+    public static void main(String[] args) {
+        int[] nums = new int[]{0,0,1,1,1,2,2,3,3,4};
+        System.out.println(removeDuplicates(nums));
+    }
+}
\ No newline at end of file
diff --git a/leetcode/27-Easy-Remove-Element/solution.java b/leetcode/27-Easy-Remove-Element/solution.java
new file mode 100644
index 0000000..0ef70ab
--- /dev/null
+++ b/leetcode/27-Easy-Remove-Element/solution.java
@@ -0,0 +1,18 @@
+import java.util.*;
+
+class Solution {
+    public int removeElement(int[] nums, int val) {
+        
+        int j = 0;
+        for(int i = 0 ; i < nums.length; i++)
+        {
+            if(nums[i] != val)
+            {
+                nums[j] = nums[i];
+                j++;
+            }
+        }
+        return j;
+        
+    }
+}
\ No newline at end of file
diff --git a/leetcode/3-Medium-Longest-Substring-Without-Repeating-Characters/Solution.java b/leetcode/3-Medium-Longest-Substring-Without-Repeating-Characters/Solution.java
new file mode 100644
index 0000000..fdcf420
--- /dev/null
+++ b/leetcode/3-Medium-Longest-Substring-Without-Repeating-Characters/Solution.java
@@ -0,0 +1,30 @@
+import java.util.*;
+class Solution {
+
+    public static int lengthOfLongestSubstring(String s) 
+    {
+    int i = 0, j = 0, max = 0;
+    HashSet<Character> set = new HashSet<>();
+    
+    while (j < s.length()) {
+        if (!set.contains(s.charAt(j))) {
+            set.add(s.charAt(j++));
+            max = Math.max(max, set.size());
+        } else {
+            set.remove(s.charAt(i++));
+        }
+    }
+    
+    return max;
+    }
+    
+    ////.................TESTING................./////
+
+    public static void main(String[] args) 
+    {
+        String s = "dvdf";
+        System.out.println("Input : "+ s);
+        System.out.println("Output : "+lengthOfLongestSubstring(s));
+
+    }
+}
diff --git a/leetcode/5-Medium-Longest-Palindromic-Substring/solution.java b/leetcode/5-Medium-Longest-Palindromic-Substring/solution.java
new file mode 100644
index 0000000..a86ffe2
--- /dev/null
+++ b/leetcode/5-Medium-Longest-Palindromic-Substring/solution.java
@@ -0,0 +1,32 @@
+class Solution {
+    public static String longestPalindrome(String s) {
+        char[] chars = s.toCharArray();
+        int len = s.length();c
+        while (len >= 0) {
+            for (int i = 0; i + len - 1 < chars.length; i++) {
+                int left = i;
+                int right = i + len - 1;
+                boolean good = true;
+                while (left < right) {
+                    if (chars[left] != chars[right]) {
+                        good = false;
+                        break;
+                    }
+                    left++;
+                    right--;
+                }
+                if (good)
+                    return s.substring(i, i + len);
+            }
+            --len;
+        }
+        
+        return "";
+           }
+    public static void main(String[] args)
+     {
+        String s = "aabbbaa";
+        System.out.println(longestPalindrome(s));
+
+    }
+}
\ No newline at end of file
diff --git a/leetcode/6-Medium-Zig-Zag-Conversion/answer.java b/leetcode/6-Medium-Zig-Zag-Conversion/answer.java
index 5e9aa12..d276189 100644
--- a/leetcode/6-Medium-Zig-Zag-Conversion/answer.java
+++ b/leetcode/6-Medium-Zig-Zag-Conversion/answer.java
@@ -5,6 +5,7 @@ public static String convert(String s, int numRows) {
 	        	return s;
         // Create string buffer to hold string buffer for each row
 	    StringBuffer[] result = new StringBuffer[numRows];
+	    // easy to maintain
 	    for (int i = 0; i < numRows; i++){
 	        result[i] = new StringBuffer();
 	    }
@@ -27,4 +28,4 @@ public static String convert(String s, int numRows) {
 	    }
 	    return result[0].toString();
 	}
-}
\ No newline at end of file
+}
diff --git a/leetcode/7-Easy-Reverse-Integer/Solution.java b/leetcode/7-Easy-Reverse-Integer/Solution.java
new file mode 100644
index 0000000..fe4c32d
--- /dev/null
+++ b/leetcode/7-Easy-Reverse-Integer/Solution.java
@@ -0,0 +1,28 @@
+class Solution {
+    public int reverse(int x) 
+    {
+        int rev = 0,n = 0 ;
+        boolean neg = false;
+        if( x < 0)
+        {
+            x = x * -1;
+            neg = true;
+        }
+        while( x > 0)
+        {
+            n = x % 10;
+            if (rev > Integer.MAX_VALUE/10 || (rev == Integer.MAX_VALUE / 10 && n > 7)) return 0;
+            if (rev < Integer.MIN_VALUE/10 || (rev == Integer.MIN_VALUE / 10 && n < -8)) return 0;
+            rev = rev * 10 + n;
+            x = x / 10;
+            
+        }
+        if(neg){ rev = -1 * rev ;}
+        return rev;
+    }
+     public static void main(String[] args)
+      {
+        Solution s = new Solution();
+        System.out.println(s.reverse(324));
+     }
+}
\ No newline at end of file
diff --git a/leetcode/8-Medium-Atoi/Solution.java b/leetcode/8-Medium-Atoi/Solution.java
new file mode 100644
index 0000000..d744a16
--- /dev/null
+++ b/leetcode/8-Medium-Atoi/Solution.java
@@ -0,0 +1,55 @@
+import java.util.*;
+
+class Solution {
+    public static int myAtoi(String str) 
+    {
+        int num = 0;
+        int d = 10, neg = 1;
+        boolean digit_occur = false;
+        for(int i = 0 ; i < str.length(); i++) {
+
+            char ch = str.charAt(i);
+            if(Character.isAlphabetic(ch) || ch == '.' || ch == '-' || ch ==' ' || ch == '+'){
+                if(digit_occur ){
+                    return neg * num;
+                }
+                else{
+                     if (ch == ' ' || ch == '+' || ch == '-'){
+                        if(i+ 1 < str.length())
+                        {
+                           if(Character.isDigit(str.charAt(i+1)))
+                           { neg = ch == '-' ? neg * -1 : neg ;}
+                            else if (ch == ' ') {
+                                continue;
+                            }
+                            else 
+                            {return neg * num;}
+                            
+                        }
+                       
+                    }
+                    else 
+                    {
+                        return neg * num;
+                    }
+                }
+            }
+            if(Character.isDigit(ch)){
+                digit_occur = true;
+                  if (num > Integer.MAX_VALUE/ 10 || num == Integer.MAX_VALUE  /10 && Integer.MAX_VALUE % 10 < (ch - '0') ) {
+                      return neg == 1 ? Integer.MAX_VALUE  : Integer.MIN_VALUE;}
+                  num = num * d + Character.getNumericValue(ch);
+            }
+            
+        }
+           
+        return neg *num;
+        
+    }
+    public static void main(String[] args) 
+    {
+    
+        String s = ".1";
+        System.out.println( myAtoi(s));
+    }
+}
\ No newline at end of file