문제 Given a string s, return the longest palindromic substring in s. A string is called a palindrome string if the reverse of that string is the same as the original string. Example 1: Input: s = "babad" Output: "bab" Explanation: "aba" is also a valid answer. Example 2: Input: s = "cbbd" Output: "bb" Constraints: 1 = 0 && y < s.length && s[x] === s[y]) { x--; y++; } // 만약 x가 -1 일 때, 혹은 만약 y가 s.l..