#3918
Medium Algorithms Sum of primes between number and its reverse
75.5% acceptance
May 13, 2026
25
2
You are given an integer n.
Let r be the integer formed by reversing the digits of n.
Return the sum of all prime numbers between min(n, r) and max(n, r), inclusive.
Solution
Rust
Time O(n²)
Space O(1)
impl Solution {
pub fn sum_of_primes_in_range(n: i32) -> i32 {
let mut r = 0i32;
let mut x = n;
while x > 0 {
r = r * 10 + x % 10;
x /= 10;
}
let lo = n.min(r);
let hi = n.max(r);
let mut sum = 0i32;
for v in lo..=hi {
if v < 2 { continue; }
let mut prime = true;
let mut d = 2;
while d * d <= v {
if v % d == 0 { prime = false; break; }
d += 1;
}
if prime { sum += v; }
}
sum
}
}