Restore IP Addresses

DIRECTORY.md

@@ -14,6 +14,7 @@
   * [Generate Parentheses](backtracking/generate_parentheses.py)
   * [Generate Parentheses Iterative](backtracking/generate_parentheses_iterative.py)
   * [Hamiltonian Cycle](backtracking/hamiltonian_cycle.py)
+  * [Ip Address](backtracking/ip_address.py)
   * [Knight Tour](backtracking/knight_tour.py)
   * [Match Word Pattern](backtracking/match_word_pattern.py)
   * [Minimax](backtracking/minimax.py)
@@ -195,6 +196,7 @@
     * [Permutations](data_structures/arrays/permutations.py)
     * [Prefix Sum](data_structures/arrays/prefix_sum.py)
     * [Product Sum](data_structures/arrays/product_sum.py)
+    * [Rotate Array](data_structures/arrays/rotate_array.py)
     * [Sparse Table](data_structures/arrays/sparse_table.py)
     * [Sudoku Solver](data_structures/arrays/sudoku_solver.py)
   * Binary Tree

backtracking/ip_address.py

@@ -0,0 +1,45 @@
+"""
+Restore IP Addresses
+-> IP Address consists of exactly four integers seperated by single dots.
+-> Each integer is between 0 and 255.
+-> Exempli Gratia - 192.168.1.1 is valid ip address but 192.168@1.1 is an invalid ip address.
+
+We are given with a string containing only digits , return all possible valid IP Addresses that
+can be formed by inserting dots in the string.
+--> Not allowed to reorder or remove any digits in the string.
+--> Return valid IP addresses in any order.
+
+Topics covered: Backtracking
+
+Example:
+Input: s = "25525511135"
+Output: ["255.255.11.135","255.255.111.35"]
+
+"""
+
+
+class Solution:
+    def restoreIpAddresses(self, s: str):
+        res = []
+
+        def backtrack(start, path):
+            # Base case: if we have 4 parts and used all digits
+            if len(path) == 4:
+                if start == len(s):
+                    res.append(".".join(path))
+                return
+
+            # Try segments of length 1 to 3
+            for l in range(1, 4):
+                if start + l > len(s):
+                    break
+                segment = s[start : start + l]
+
+                # Skip invalid parts (leading zeros or > 255)
+                if (segment.startswith("0") and len(segment) > 1) or int(segment) > 255:
+                    continue
+
+                backtrack(start + l, path + [segment])
+
+        backtrack(0, [])
+        return res