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LeetCode 866: Prime Palindrome

Problem Restatement We are given an integer n . We need to return the smallest integer greater than or equal to n that is both: Prime A palindrome A prime number has exactly two divisors: 1 and itself A palindrome reads the same from left to right and right to left. For example: 101 131 929 The answer is guaranteed to exist in the range: [2, 2 * 10^8] Input...

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LeetCode 647: Palindromic Substrings

Problem Restatement We are given a string s . We need to count how many substrings of s are palindromes. A palindrome reads the same forward and backward. A substring is a contiguous part of the string. The same text can be counted multiple times if it appears at different positions. For example, in "aaa" , each "a" at each index is counted separately. The constraints are 1 <= s.length...

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LeetCode 906: Super Palindromes

Problem Restatement A positive integer is called a super-palindrome if: The number itself is a palindrome. It is the square of another palindrome. We are given two positive integers left and right as strings. Return how many super-palindromes are in the inclusive range: [left, right] For example, 9 is a super-palindrome because: 9 = 3 * 3 and both 9 and 3 are palindromes. The official problem uses string inputs...

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LeetCode 730: Count Different Palindromic Subsequences

Problem Restatement We are given a string s . We need to count how many different non-empty palindromic subsequences appear in s . A subsequence is made by deleting zero or more characters without changing the order of the remaining characters. A palindrome reads the same forward and backward. The answer can be large, so we return it modulo: 10**9 + 7 The string contains only the characters 'a' ,...

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LeetCode 564: Find the Closest Palindrome

Problem Restatement We are given a string n representing an integer. Return the closest integer palindrome to n . The returned palindrome must not be n itself. If there are two palindromes with the same distance from n , return the smaller one. The input length is at most 18 , so the number can be too large for some fixed-width integer languages, but Python can handle it directly. The...

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LeetCode 214: Shortest Palindrome

Problem Restatement We are given a string s . We may add characters only in front of s . We need to return the shortest palindrome that can be created this way. The official statement says we can convert s to a palindrome by adding characters in front of it, and we must return the shortest palindrome possible. Input and Output Item Meaning Input String s Output Shortest palindrome formed...

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LeetCode 132: Palindrome Partitioning II

Problem Restatement We are given a string s . We need to cut the string into substrings so that every substring is a palindrome. Return the minimum number of cuts needed. LeetCode states the problem as partitioning s so every substring is a palindrome, then returning the minimum cuts needed for such a palindrome partitioning. The constraints are 1 <= s.length <= 2000 , and s contains lowercase English letters...

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LeetCode 479: Largest Palindrome Product

Problem Restatement We are given an integer n . We need to find the largest palindrome that can be written as the product of two n -digit integers. Because the answer may be very large, we return the palindrome modulo 1337 . For example, when n = 2 , the two-digit numbers are from 10 to 99 . The largest palindrome product is: 99 * 91 = 9009 Then we...

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LeetCode 5: Longest Palindromic Substring

Problem Restatement We are given a string s . We need to return the longest substring that is a palindrome. A palindrome reads the same forward and backward. Examples: "aba" "racecar" "bb" All of these are palindromes. A substring must be contiguous. For example: "aceca" is a substring of "racecar" . But: "rcar" is not contiguous, so it is not a substring. The problem asks for the substring itself, not...

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