https://leetcode.com/problems/restore-ip-addresses/

Author: harshitgindra

MediumProblems/RestoreIpAddress.cs

@@ -0,0 +1,32 @@
+namespace LeetCode.MediumProblems;
+
+/// <summary>
+/// https://leetcode.com/problems/restore-ip-addresses/
+/// </summary>
+public class RestoreIpAddress
+{
+    public IList<string> RestoreIpAddresses(string s) {
+        List<string> result = new List<string>();
+        if (s.Length < 4 || s.Length > 12) return result;
+        Backtrack(s, 0, new List<string>(), result);
+        return result;
+    }
+    
+    private void Backtrack(string s, int start, List<string> currentSegments, List<string> result) {
+        if (currentSegments.Count == 4 && start == s.Length) {
+            result.Add(string.Join(".", currentSegments));
+            return;
+        }
+        if (currentSegments.Count == 4 || start >= s.Length) return;
+        
+        for (int len = 1; len <= 3; len++) {
+            if (start + len > s.Length) break;
+            string segment = s.Substring(start, len);
+            if (segment[0] == '0' && segment.Length > 1) continue;
+            if (int.Parse(segment) > 255) continue;
+            currentSegments.Add(segment);
+            Backtrack(s, start + len, currentSegments, result);
+            currentSegments.RemoveAt(currentSegments.Count - 1);
+        }
+    }
+}