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Added Longest Palindromic subsequence #449

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Merged
pomkarnath98 merged 2 commits into from
Oct 10, 2020
Merged

Added Longest Palindromic subsequence #449

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44afa53
Added Longest Plaindromic subsequence
suhailmalik07 Oct 10, 2020
4c0ca3c
Fixes Standard
suhailmalik07 Oct 10, 2020
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39 changes: 39 additions & 0 deletions Dynamic-Programming/LongestPalindromicSubsequence.js
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Original file line number Diff line number Diff line change
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/*
LeetCode -> https://leetcode.com/problems/longest-palindromic-subsequence/

Given a string s, find the longest palindromic subsequence's length in s.
You may assume that the maximum length of s is 1000.

*/

const longestPalindromeSubsequence = function (s) {
const n = s.length

const dp = new Array(n).fill(0).map(item => new Array(n).fill(0).map(item => 0))

// fill predefined for single character
for (let i = 0; i < n; i++) {
dp[i][i] = 1
}

for (let i = 1; i < n; i++) {
for (let j = 0; j < n - i; j++) {
const col = j + i
if (s[j] === s[col]) {
dp[j][col] = 2 + dp[j + 1][col - 1]
} else {
dp[j][col] = Math.max(dp[j][col - 1], dp[j + 1][col])
}
}
}

return dp[0][n - 1]
}

const main = () => {
console.log(longestPalindromeSubsequence('bbbab')) // 4
console.log(longestPalindromeSubsequence('axbya')) // 3
console.log(longestPalindromeSubsequence('racexyzcxar')) // 7
}

main()