From 050c383c1f91094fcbaf56791f9cb583b9ab7d80 Mon Sep 17 00:00:00 2001
From: YOGESH CHAND UPADHYAY <84492118+yogesh-9999@users.noreply.github.com>
Date: Thu, 13 Oct 2022 23:26:56 +0530
Subject: [PATCH 1/2] LongestpalindromicSubstring in Java and python

---
 .../solutionInJava.java                       | 36 +++++++++++++++++++
 .../solutioninpython.py                       | 27 ++++++++++++++
 2 files changed, 63 insertions(+)
 create mode 100644 Leetcode-Medium/5-LongestPalindromicSubstring/solutionInJava.java
 create mode 100644 Leetcode-Medium/5-LongestPalindromicSubstring/solutioninpython.py

diff --git a/Leetcode-Medium/5-LongestPalindromicSubstring/solutionInJava.java b/Leetcode-Medium/5-LongestPalindromicSubstring/solutionInJava.java
new file mode 100644
index 0000000..08d4473
--- /dev/null
+++ b/Leetcode-Medium/5-LongestPalindromicSubstring/solutionInJava.java
@@ -0,0 +1,36 @@
+class Solution {
+    public String longestPalindrome(String s) {
+        char[] sChars = s.toCharArray();
+
+        int m = s.length();
+
+        // * dp[i][len + 1] means substring starting from i with length of len;
+        boolean[][] dp = new boolean[m][2];
+        int currCol = 0;
+
+        int maxLen = 0;
+        int ans = 0; // record start index of s
+
+        for (int len = 0; len < m; len++) {
+            for (int start = 0; start + len < m; start++) {
+                int end = start + len;
+                if (len == 0) {
+                    dp[start][currCol] = true;
+                } else if (len == 1) {
+                    dp[start][currCol] = (sChars[start] == sChars[end]);
+                } else {
+                    dp[start][currCol] = (sChars[start] == sChars[end] && dp[start + 1][currCol]);
+                }
+
+                if (dp[start][currCol] && len + 1 > maxLen) {
+                    ans = start;
+                    maxLen = len + 1;
+                }
+            }
+
+            currCol = 1 - currCol;
+        }
+
+        return maxLen == 0 ? "" : s.substring(ans, ans + maxLen);
+    }
+}
\ No newline at end of file
diff --git a/Leetcode-Medium/5-LongestPalindromicSubstring/solutioninpython.py b/Leetcode-Medium/5-LongestPalindromicSubstring/solutioninpython.py
new file mode 100644
index 0000000..7211d13
--- /dev/null
+++ b/Leetcode-Medium/5-LongestPalindromicSubstring/solutioninpython.py
@@ -0,0 +1,27 @@
+class Solution:
+    def longestPalindrome(self, s: str) -> str:
+        
+        n = len(s)
+        # Form a bottom-up dp 2d array
+        # dp[i][j] will be 'true' if the string from index i to j is a palindrome. 
+        dp = [[False] * n  for _ in range(n)]
+        
+        ans = ''
+        # every string with one character is a palindrome
+        for i in range(n):
+            dp[i][i] = True
+            ans = s[i]
+            
+        maxLen = 1
+        for start in range(n-1, -1, -1):
+            for end in range(start+1, n):             
+				# palindrome condition
+                if s[start] == s[end]:
+                    # if it's a two char. string or if the remaining string is a palindrome too
+                    if end - start == 1 or dp[start+1][end-1]:
+                        dp[start][end] = True
+                        if maxLen < end - start + 1:
+                            maxLen = end - start + 1
+                            ans = s[start: end+ 1]
+        
+        return ans
\ No newline at end of file

From 8e9ca110a3bf8ad5a8c75cbdfc31bb0e57e56a4a Mon Sep 17 00:00:00 2001
From: YOGESH CHAND UPADHYAY <84492118+yogesh-9999@users.noreply.github.com>
Date: Thu, 13 Oct 2022 23:32:19 +0530
Subject: [PATCH 2/2] added Java solution for validtae stack sequences in Java

---
 .../946-validate-stack-sequences/solution.java       | 12 ++++++++++++
 1 file changed, 12 insertions(+)
 create mode 100644 Leetcode-Medium/946-validate-stack-sequences/solution.java

diff --git a/Leetcode-Medium/946-validate-stack-sequences/solution.java b/Leetcode-Medium/946-validate-stack-sequences/solution.java
new file mode 100644
index 0000000..484b1ab
--- /dev/null
+++ b/Leetcode-Medium/946-validate-stack-sequences/solution.java
@@ -0,0 +1,12 @@
+public boolean validateStackSequences(int[] pushed, int[] popped) {
+    Stack<Integer> stack = new Stack<>();
+    int i = 0;
+    for (int x : pushed) {
+        stack.push(x);
+        while (!stack.empty() && stack.peek() == popped[i]) {
+            stack.pop();
+            i++;
+        }
+    }
+    return stack.empty();
+}
\ No newline at end of file