Add problem 2501: Longest Square Streak in an Array

Author: EFanZh

Diff for: src/lib.rs

@@ -1871,6 +1871,7 @@ pub mod problem_2496_maximum_value_of_a_string_in_an_array;
 pub mod problem_2497_maximum_star_sum_of_a_graph;
 pub mod problem_2498_frog_jump_ii;
 pub mod problem_2500_delete_greatest_value_in_each_row;
+pub mod problem_2501_longest_square_streak_in_an_array;
 
 #[cfg(test)]
 mod test_utilities;

Diff for: src/problem_2501_longest_square_streak_in_an_array/dynamic_programming.rs

@@ -0,0 +1,46 @@
+pub struct Solution;
+
+// ------------------------------------------------------ snip ------------------------------------------------------ //
+
+use std::collections::HashMap;
+
+impl Solution {
+    pub fn longest_square_streak(nums: Vec<i32>) -> i32 {
+        let mut nums = nums.into_iter().map(|x| x as u32).collect::<Vec<_>>();
+
+        nums.sort_unstable_by(|lhs, rhs| rhs.cmp(lhs));
+
+        let mut lengths = HashMap::new();
+        let mut result = 0_u32;
+
+        for num in nums {
+            let length = num
+                .checked_mul(num)
+                .and_then(|squared| lengths.get(&squared))
+                .copied()
+                .unwrap_or(0)
+                + 1;
+
+            lengths.insert(num, length);
+            result = result.max(length);
+        }
+
+        if result < 2 { -1 } else { result as _ }
+    }
+}
+
+// ------------------------------------------------------ snip ------------------------------------------------------ //
+
+impl super::Solution for Solution {
+    fn longest_square_streak(nums: Vec<i32>) -> i32 {
+        Self::longest_square_streak(nums)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    #[test]
+    fn test_solution() {
+        super::super::tests::run::<super::Solution>();
+    }
+}

Diff for: src/problem_2501_longest_square_streak_in_an_array/mod.rs

@@ -0,0 +1,18 @@
+pub mod dynamic_programming;
+
+pub trait Solution {
+    fn longest_square_streak(nums: Vec<i32>) -> i32;
+}
+
+#[cfg(test)]
+mod tests {
+    use super::Solution;
+
+    pub fn run<S: Solution>() {
+        let test_cases = [(&[4, 3, 6, 16, 8, 2] as &[_], 3), (&[2, 3, 5, 6, 7], -1)];
+
+        for (nums, expected) in test_cases {
+            assert_eq!(S::longest_square_streak(nums.to_vec()), expected);
+        }
+    }
+}