[LeetCode] 5. Longest Palindromic Substring (Medium)

#5. Longest Palindromic Substring Medium

문제

주어진 문자열 s에서 가장 긴 회문을 반환하는 문제입니다.

답

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var longestPalindrome = function(s) {
    let longest = '';
    const findLongestPalindrome = (str, i, j) => {
        while(i >= 0 && j < str.length && str[i] === str[j]) {
            i -= 1;
            j += 1;
        }
        // slice the qualified substring from the second last iteration
        return str.slice(i + 1, j);
    }
    for (let i = 0; i < s.length; i++) {
        // palindrome can center around 1 or 2 letters
        const current1 = findLongestPalindrome(s, i, i);
        const current2 = findLongestPalindrome(s, i, i + 1);
        const longerPalindrome = 
              current1.length > current2.length ? current1 : current2;
        if (longerPalindrome.length > longest.length) {
            longest = longerPalindrome;
        } 
    }
    return longest;
};

설명

LeetCode

Given a string s, return the longest palindromic substring in s.

Example 1:

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Input: s = "babad"
Output: "bab"
Note: "aba" is also a valid answer.

Example 2:

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Input: s = "cbbd"
Output: "bb"

Example 3:

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Input: s = "a"
Output: "a"

Example 4:

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Input: s = "ac"
Output: "a"

Constraints:

1 <= s.length <= 1000
s consist of only digits and English letters (lower-case and/or upper-case),