Super palindromes

Math String Enumeration

39.8% acceptance

Feb 25, 2026

376

423

Let's say a positive integer is a super-palindrome if it is a palindrome, and it is also the square of a palindrome. Given two positive integers left and right represented as strings, return the number of super-palindromes integers in the inclusive range [left, right].

Solution

Rust

Time O(n)

Space O(1)

LeetCode

solution.rs

impl Solution {
  pub fn superpalindromes_in_range(left: String, right: String) -> i32 {
    let lo: i64 = left.parse().unwrap();
    let hi: i64 = right.parse().unwrap();
    let mut count = 0;
    let is_pal = |s: &str| -> bool { s.as_bytes() == s.as_bytes().iter().rev().cloned().collect::<Vec<u8>>() };
    // Odd-length palindromes: k -> k + reverse(k without last digit)
    for k in 1..100_001i64 {
      let s = k.to_string();
      let rev: String = s[..s.len()-1].chars().rev().collect();
      let p: i64 = format!("{}{}", s, rev).parse().unwrap();
      let p2 = p * p;
      if p2 > hi { break; }
      if p2 >= lo && is_pal(&p2.to_string()) { count += 1; }
    }
    // Even-length palindromes: k -> k + reverse(k)
    for k in 1..100_001i64 {
      let s = k.to_string();
      let rev: String = s.chars().rev().collect();
      let p: i64 = format!("{}{}", s, rev).parse().unwrap();
      let p2 = p * p;
      if p2 > hi { break; }
      if p2 >= lo && is_pal(&p2.to_string()) { count += 1; }
    }
    count
  }
}