Add problem 2761: Prime Pairs With Target Sum

Author: EFanZh

src/lib.rs

@@ -1959,6 +1959,7 @@ pub mod problem_2739_total_distance_traveled;
 pub mod problem_2740_find_the_value_of_the_partition;
 pub mod problem_2744_find_maximum_number_of_string_pairs;
 pub mod problem_2760_longest_even_odd_subarray_with_threshold;
+pub mod problem_2761_prime_pairs_with_target_sum;
 
 #[cfg(test)]
 mod test_utilities;

src/problem_2761_prime_pairs_with_target_sum/mod.rs

@@ -0,0 +1,18 @@
+pub mod sieve_of_eratosthenes;
+
+pub trait Solution {
+    fn find_prime_pairs(n: i32) -> Vec<Vec<i32>>;
+}
+
+#[cfg(test)]
+mod tests {
+    use super::Solution;
+
+    pub fn run<S: Solution>() {
+        let test_cases = [(10, &[[3, 7], [5, 5]] as &[_]), (2, &[])];
+
+        for (n, expected) in test_cases {
+            assert_eq!(S::find_prime_pairs(n), expected);
+        }
+    }
+}

src/problem_2761_prime_pairs_with_target_sum/sieve_of_eratosthenes.rs

@@ -0,0 +1,50 @@
+pub struct Solution;
+
+// ------------------------------------------------------ snip ------------------------------------------------------ //
+
+impl Solution {
+    pub fn find_prime_pairs(n: i32) -> Vec<Vec<i32>> {
+        let n = n as u32 as usize;
+        let mut result = Vec::new();
+
+        if n >= 4 {
+            let mut is_composites = vec![false; n - 3].into_boxed_slice();
+
+            for step in 2..=n.isqrt() {
+                if !is_composites[step - 2] {
+                    let mut i = step * step - 2;
+
+                    while let Some(is_composite) = is_composites.get_mut(i) {
+                        *is_composite = true;
+                        i += step;
+                    }
+                }
+            }
+
+            result.extend(
+                (2..)
+                    .zip(is_composites[..n / 2 - 1].iter().zip(is_composites.iter().rev()))
+                    .filter(|&(_, (&lhs_is_composite, &rhs_is_composite))| !lhs_is_composite && !rhs_is_composite)
+                    .map(|(lhs, _)| vec![lhs, n as i32 - lhs]),
+            );
+        }
+
+        result
+    }
+}
+
+// ------------------------------------------------------ snip ------------------------------------------------------ //
+
+impl super::Solution for Solution {
+    fn find_prime_pairs(n: i32) -> Vec<Vec<i32>> {
+        Self::find_prime_pairs(n)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    #[test]
+    fn test_solution() {
+        super::super::tests::run::<super::Solution>();
+    }
+}