public class Solution {
    private class Node {
        public Dictionary<char, Node> Next { get; set; } = new();
        public bool Has { get; set; } = false;

        public Node() { }
    }

    private static Node MakeTrie(string[] dictionary) {
        var root = new Node();

        foreach (var word in dictionary) {
            var node = root;
            foreach (var c in word) {
                if (!node.Next.ContainsKey(c)) {
                    node.Next[c] = new();
                }
                node = node.Next[c];
            }
            node.Has = true;
        }

        return root;
    }

    public int MinExtraChar(string s, string[] dictionary) {
        var trie = MakeTrie(dictionary);

        var length = s.Length;
        var dp = new int[length + 1];

        for (var start = length - 1; start >= 0; --start) {
            dp[start] = 1 + dp[start + 1];

            var node = trie;
            for (var end = start; end < length; ++end) {
                if (!node.Next.ContainsKey(s[end])) {
                    break;
                }

                node = node.Next[s[end]];
                if (node.Has) {
                    dp[start] = Math.Min(dp[start], dp[end + 1]);
                }
            }
        }

        return dp[0];
    }
}