From 5d40a9cbd4e4241784d8e1b9ce17a9888a1d5845 Mon Sep 17 00:00:00 2001
From: Matej Focko <me@mfocko.xyz>
Date: Mon, 23 Sep 2024 23:11:04 +0200
Subject: [PATCH] =?UTF-8?q?cs:=20add=20=C2=AB2707.=20Extra=20Characters=20?=
 =?UTF-8?q?in=20a=20String=C2=BB?=
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Signed-off-by: Matej Focko <me@mfocko.xyz>
---
 cs/extra-characters-in-a-string.cs | 50 ++++++++++++++++++++++++++++++
 1 file changed, 50 insertions(+)
 create mode 100644 cs/extra-characters-in-a-string.cs

diff --git a/cs/extra-characters-in-a-string.cs b/cs/extra-characters-in-a-string.cs
new file mode 100644
index 0000000..e07702d
--- /dev/null
+++ b/cs/extra-characters-in-a-string.cs
@@ -0,0 +1,50 @@
+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];
+    }
+}