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added Longest Palindromic Substring (Medium)

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	`1`	`+# Longest Palindromic Substring`
	`2`	`+`
	`3`	`+[Leetcode Link](https://leetcode.com/problems/longest-palindromic-substring/)`
	`4`	`+`
	`5`	`+## Problem:`
	`6`	`+`
	`7`	+Given a string `s`, return the longest palindromic substring in `s`.
	`8`	`+`
	`9`	`+## Example:`
	`10`	`+`
	`11`	+```
	`12`	`+Input: s = "babad"`
	`13`	`+Output: "bab"`
	`14`	`+Note: "aba" is also a valid answer.`
	`15`	+```
	`16`	`+`
	`17`	+```
	`18`	`+Input: s = "cbbd"`
	`19`	`+Output: "bb"`
	`20`	+```
	`21`	`+`
	`22`	+```
	`23`	`+Input: s = "a"`
	`24`	`+Output: "a"`
	`25`	+```
	`26`	`+`
	`27`	+```
	`28`	`+Input: s = "ac"`
	`29`	`+Output: "a"`
	`30`	+```
	`31`	`+`
	`32`	`+## Note:`
	`33`	`+`
	`34`	`+- 1 <= s.length <= 1000`
	`35`	`+- s consist of only digits and English letters (lower-case and/or upper-case),`

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	`1`	`+`
	`2`	`+class Solution:`
	`3`	`+ def longestPalindrome(self, s: str) -> str:`
	`4`	`+ N = len(s)`
	`5`	`+ longestLength = 0`
	`6`	`+ left = 0`
	`7`	`+ right = 0`
	`8`	`+ # create N x N dynamic programming table and init with setting i==j true`
	`9`	`+ # because a word of length 1 is always palindromic`
	`10`	`+ dp = [[False for n in range(N)] for n in range(N)]`
	`11`	`+ for i in range(N):`
	`12`	`+ dp[i][i] = True`
	`13`	`+ # print(dp)`
	`14`	`+ # bottom-up fill-in`
	`15`	`+ # if length of 2 -> palindromic iff two letters are same`
	`16`	`+ # if longer length -> palindromic iff start and end letters are same AND`
	`17`	`+ # inner word is palindromic (check for [i+1][j-1])`
	`18`	`+ for i in range(N-2, -1, -1):`
	`19`	`+ for j in range(N-1, i-1, -1):`
	`20`	`+ if i == j-1:`
	`21`	`+ if s[i] == s[j]:`
	`22`	`+ dp[i][j] = s[i] == s[j]`
	`23`	`+ else:`
	`24`	`+ if s[i] == s[j] and dp[i+1][j-1]:`
	`25`	`+ dp[i][j] = True`
	`26`	`+ if dp[i][j]:`
	`27`	`+ if j-i+1 > longestLength:`
	`28`	`+ # new longest palindromic substring, so update`
	`29`	`+ longestLength = j-i+1`
	`30`	`+ left = i`
	`31`	`+ right = j`
	`32`	`+ break`
	`33`	`+ print(dp)`
	`34`	`+ return s[left:right+1]`
	`35`	`+`
	`36`	`+`
	`37`	`+sol = Solution()`
	`38`	`+s = "babad"`
	`39`	`+print(sol.longestPalindrome(s))`

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`@@ -47,6 +47,7 @@ Languages used: Java and Python`
`47`	`47`	`- [Merge Two Binary Trees](Easy/MergeTwoBinaryTrees)`
`48`	`48`	`- [Invert Binary Tree](Easy/InvertBinaryTree)`
`49`	`49`	`- Medium`
	`50`	`+`
`50`	`51`	`- [Minimum Add to Make Parentheses Valid](Medium/MinimumAddtoMakeParenthesesValid)`
`51`	`52`	`- [Distribute Coins in Binary Tree](Medium/DistributeCoinsInBinaryTree)`
`52`	`53`	`- [Find Minimum Number of Fibonacci Numbers Whose Sum is K](Medium/FindMinNumFibNumSumK)`
`@@ -96,6 +97,8 @@ Languages used: Java and Python`
`96`	`97`	`- [Permutations](Medium/Permutations)`
`97`	`98`	`- [Permutations II](Medium/Permutations2)`
`98`	`99`	`- [Combinations](Medium/Combinations)`
	`100`	`+ - [Longest Palindromic Substring](Medium/LongestPalindromicSubstring)`
	`101`	`+`
`99`	`102`	`- Hard`
`100`	`103`
`101`	`104`	`- [Maximum Score Words Formed by Letters](Hard/MaximumScoreWords)`

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