adding longestpalindromicSubstring

.vscode/settings.json

@@ -0,0 +1,3 @@
+{
+    "java.debug.settings.onBuildFailureProceed": true
+}

Leetcode/logestPalindromicSubstring.java

@@ -1,4 +1,32 @@
-class logestPalindromicSubstring {
+package Leetcode;
+/**
+ * Given a string s, return the longest 
+palindromic
+ 
+substring
+ in s.
+
+ 
+
+Example 1:
+
+Input: s = "babad"
+Output: "bab"
+Explanation: "aba" is also a valid answer.
+Example 2:
+
+Input: s = "cbbd"
+Output: "bb"
+ 
+
+Constraints:
+
+1 <= s.length <= 1000
+s consist of only digits and English letters.
+ */
+
+public class logestPalindromicSubstring {
+
     public String longestPalindrome(String s) {
 
          if (s.length() <= 1) {
@@ -34,4 +62,9 @@ public String longestPalindrome(String s) {
 
         return maxStr;
     }
+
+    public static void main(String[] args) {
+        logestPalindromicSubstring lps = new logestPalindromicSubstring();
+        System.out.println(lps.longestPalindrome("babad"));
+    }
 }

Leetcode/zigzag.java

@@ -0,0 +1,99 @@
+package Leetcode;
+
+/**
+ * 
+ * 
+ * The string "PAYPALISHIRING" is written in a zigzag pattern on a given number of rows like this: (you may want to display this pattern in a fixed font for better legibility)
+
+P   A   H   N
+A P L S I I G
+Y   I   R
+And then read line by line: "PAHNAPLSIIGYIR"
+
+Write the code that will take a string and make this conversion given a number of rows:
+
+string convert(string s, int numRows);
+ 
+
+Example 1:
+
+Input: s = "PAYPALISHIRING", numRows = 3
+Output: "PAHNAPLSIIGYIR"
+Example 2:
+
+Input: s = "PAYPALISHIRING", numRows = 4
+Output: "PINALSIGYAHRPI"
+Explanation:
+P     I    N
+A   L S  I G
+Y A   H R
+P     I
+Example 3:
+
+Input: s = "A", numRows = 1
+Output: "A"
+ 
+
+Constraints:
+
+1 <= s.length <= 1000
+s consists of English letters (lower-case and upper-case), ',' and '.'.
+1 <= numRows <= 1000
+ * 
+ */
+public class zigzag {
+
+    public String convert(String s, int numRows) {
+        //if number of rows is one then return as is
+        if(numRows<=1) return s;
+        // create array to store string row wise
+        String[] a = new String[numRows];
+        //flag to check if to go from top down or bottom up
+        boolean forward = true;
+        //row count for array
+        int rowcount=0;
+
+        for(int i=0;i<numRows;i++){
+            a[i]="";
+        }
+        for(int i=0;i<s.length();i++){
+            //if forward then in each index keep on adding the character and incrementing the rowcount else add ad decrement the rowcount
+            if(forward){
+                a[rowcount]=a[rowcount]+s.charAt(i);
+                rowcount++;
+            }
+            else{
+                a[rowcount]=a[rowcount]+s.charAt(i);
+                rowcount--;
+            }
+            // if the rowcount of array is equal max number of rows we have to start decrementing the rowci-ount
+            if(rowcount==numRows ){
+                //if more than 2 rows then we will make it false else itll be always true;
+                if(numRows>2){
+                    forward=false;
+                }
+                rowcount=rowcount-2;
+            }
+            // if the rowcount is 0 and its still going bottom up then we have to reverse it.
+            else if(rowcount==0 && !forward){
+                forward=true;
+            }
+
+
+        }
+
+        String toRetrun = "";
+        for(int i=0;i<numRows;i++){
+            toRetrun=toRetrun+a[i];
+        }
+
+        return toRetrun;
+
+
+    }
+
+    public static void main(String[] args) {
+        zigzag zz = new zigzag();
+        System.out.println(zz.convert("ABCD", 2));
+    }
+}