diff --git a/src/problem/mod.rs b/src/problem/mod.rs
index 55c91fa..02a6878 100644
--- a/src/problem/mod.rs
+++ b/src/problem/mod.rs
@@ -58,4 +58,5 @@ mod p2476_closest_nodes_queries_in_a_binary_search_tree;
 mod p938_range_sum_of_bst;
 mod p889_construct_binary_tree_from_preorder_and_postorder_traversal;
 mod p2867_count_valid_paths_in_a_tree;
-mod p2673_make_costs_of_paths_equal_in_a_binary_tree;
\ No newline at end of file
+mod p2673_make_costs_of_paths_equal_in_a_binary_tree;
+mod p2581_count_number_of_possible_root_nodes;
\ No newline at end of file
diff --git a/src/problem/p2581_count_number_of_possible_root_nodes.rs b/src/problem/p2581_count_number_of_possible_root_nodes.rs
new file mode 100644
index 0000000..5cc1659
--- /dev/null
+++ b/src/problem/p2581_count_number_of_possible_root_nodes.rs
@@ -0,0 +1,106 @@
+use std::usize;
+
+/**
+ * [2581] Count Number of Possible Root Nodes
+ */
+pub struct Solution {}
+
+
+// submission codes start here
+
+use std::collections::HashSet;
+
+impl Solution {
+    pub fn root_count(edges: Vec<Vec<i32>>, guesses: Vec<Vec<i32>>, k: i32) -> i32 {
+        let mut graph = vec![vec![];edges.len() + 1];
+
+        for edge in edges {
+            let x = edge[0] as usize;
+            let y = edge[1] as usize;
+
+            graph[x].push(y);
+            graph[y].push(x);
+        }
+
+        let mut guess_set = HashSet::with_capacity(guesses.len());
+        for guess in guesses {
+            guess_set.insert(Solution::hash(
+                guess[0] as usize, 
+                guess[1] as usize));
+        }
+        
+        let mut count = 0;
+        Solution::dfs(&graph, &guess_set, 0, usize::MAX, &mut count);
+        dbg!(count);
+        
+        let mut result = 0;
+        Solution::tree_dp(&graph, &guess_set, &k, 0, 
+            usize::MAX, count, &mut result);
+        
+        result
+    }
+
+    fn hash(x: usize, y: usize) -> i64 {
+        (x as i64) * 1000000 + (y as i64)
+    }
+
+    fn dfs(graph: &Vec<Vec<usize>>, guess_set: &HashSet<i64>, now: usize, pre: usize, count: &mut i32) {
+        for next in &graph[now] {
+            let next = *next;
+            if next == pre {
+                continue;
+            }
+
+            if guess_set.contains(&Solution::hash(now, next)) {
+                *count += 1;
+            }
+
+            Solution::dfs(graph, guess_set, next, now, count);
+        }
+    }
+
+    fn tree_dp(graph: &Vec<Vec<usize>>, guess_set: &HashSet<i64>, k: &i32,
+        now: usize, pre: usize, count: i32, result: &mut i32) {
+        if count >= *k {
+            *result += 1;
+        }
+
+        for next in &graph[now] {
+            let next = *next;
+            if next == pre {
+                continue;
+            }
+
+            let mut count = count;
+            if guess_set.contains(&Solution::hash(now, next)) {
+                count -= 1;
+            }
+
+            if guess_set.contains(&Solution::hash(next, now)) {
+                count += 1;
+            }
+            
+            Solution::tree_dp(graph, guess_set, k, next, now, count, result);
+        }
+    }
+}
+
+// submission codes end
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_2581() {
+        assert_eq!(
+            Solution::root_count(
+                vec![vec![0,1],vec![1,2],vec![1,3],vec![4,2]],
+                vec![vec![1,3],vec![0,1],vec![1,0],vec![2,4]], 3), 3);
+
+        assert_eq!(
+            Solution::root_count(
+                vec![vec![0,1],vec![2,0],vec![0,3],vec![4,2],vec![3,5],vec![6,0],vec![1,7],vec![2,8],vec![2,9],vec![4,10],vec![9,11],vec![3,12],vec![13,8],vec![14,9],vec![15,9],vec![10,16]], 
+                vec![vec![8,2],vec![12,3],vec![0,1],vec![16,10]], 2), 4);
+    }
+}