Restore IP Addresses

Medium

Backtracking · String~25m

00:00

Section 1Understand Problem

Section 01

Understand the problem

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Problem statement

A valid IP address consists of exactly four integers separated by single dots. Each integer is between `0` and `255` (inclusive) and cannot have leading zeros. For example, `"0.1.2.201"` and `"192.168.1.1"` are valid IP addresses, but `"0.011.255.245"`, `"192.168.1.312"` and `"192.168@1.1"` are not. Given a string `s` containing only digits, return all possible valid IP addresses that can be formed by inserting dots into `s`. You are not allowed to reorder or remove any digits in `s`. You may return the valid IP addresses in any order.

Example

s = "25525511135" → ["255.255.11.135","255.255.111.35"]

Constraints

1 ≤ s.length ≤ 20 · s consists of digits only

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