LeetCode in Swift: Longest Palindromic Substring

Problem Statement

Given a string S, find the longest palindromic substring in S. You may assume that the maximum length of S is 1000, and there exists one unique longest palindromic substring.

Original LeetCode problem page

My Solution in Swift

An array of palindrome lengths centred at previous locations is used to make my solution run in linear time O(n)

Check this out if you need to know more about this algorithm: http://leetcode.com/2011/11/longest-palindromic-substring-part-ii.html

Try It Yourself

1: each links to a blog post of mine that is dedicated to the problem
2: total execution time of a solution on my MacBook Pro (Late 2013, 2.6 GHz Intel Core i7, 16 GB 1600 MHz DDR3). Each solution is compiled with following command:

$ swiftc -O -sdk `xcrun --show-sdk-path --sdk macosx` json.swift main.swift -o mySolution

The total execution time is the average of 10 runs.
3: these test cases are semi-automatically :P retrieved from LeetCode Online Judge system and are kept in JSON format
4: each Xcode project includes everything (my Swift solution to a problem, its JSON test cases and a driver code to test the solution on those test cases)

Problem1Time2Test Cases3My Xcode Project4
Longest Palindromic Substring2.413ms Save  (547) Save  (499)

More Problems Solved in Swift

My full list of LeetCode problems attempted using Swift