Solution: Restore IP Addresses
Explore how to apply backtracking techniques to restore valid IP addresses from a digit-only string. Learn to efficiently place dots to form valid segments, validate each segment's range, and prune invalid paths. This lesson helps you understand segment validation, recursion with constraints, and optimized combinatorial search for IP address restoration.
Statement
A valid IP address consists of four numeric segments separated by single dots. Each segment must be an integer between 0 and 255 (inclusive), and leading zeros are not allowed unless the segment is exactly ‘0.”
For instance, “10.0.1.25” and “172.16.0.5” are valid IP addresses, while “01.200.100.3,” “256.100.50.25,” and “172.16.0.500” are invalid.
Given a string s made up of digits only, return all possible valid IP addresses that can be created by inserting exactly three dots into the string. You cannot rearrange or delete any digits. The resulting list of valid IP addresses can be returned in any order.
Constraints:
The input string
sconsists of digits only.s.length
Naive approach
The naive approach would be to check all possible positions of the dots. Because an IP address requires inserting three dots, and if the input string contains