LeetCode 2781. Length of the Longest Valid Substring Solution in Java, C++, Python & More | Explanation + Code

Description

You are given a string word and an array of strings forbidden.

A string is called valid if none of its substrings are present in forbidden.

Return the length of the longest valid substring of the string word.

A substring is a contiguous sequence of characters in a string, possibly empty.

 

Example 1:

Input: word = "cbaaaabc", forbidden = ["aaa","cb"]
Output: 4
Explanation: There are 11 valid substrings in word: "c", "b", "a", "ba", "aa", "bc", "baa", "aab", "ab", "abc" and "aabc". The length of the longest valid substring is 4. 
It can be shown that all other substrings contain either "aaa" or "cb" as a substring. 

Example 2:

Input: word = "leetcode", forbidden = ["de","le","e"]
Output: 4
Explanation: There are 11 valid substrings in word: "l", "t", "c", "o", "d", "tc", "co", "od", "tco", "cod", and "tcod". The length of the longest valid substring is 4.
It can be shown that all other substrings contain either "de", "le", or "e" as a substring. 

 

Constraints:

• 1 <= word.length <= 105
• word consists only of lowercase English letters.
• 1 <= forbidden.length <= 105
• 1 <= forbidden[i].length <= 10
• forbidden[i] consists only of lowercase English letters.

Solutions

Solution 1

PythonJavaC++GoTypeScript

class Solution: def longestValidSubstring(self, word: str, forbidden: List[str]) -> int: s = set(forbidden) ans = i = 0 for j in range(len(word)): for k in range(j, max(j - 10, i - 1), -1): if word[k : j + 1] in s: i = k + 1 break ans = max(ans, j - i + 1) return ans(code-box)

class Solution { public int longestValidSubstring(String word, List<String> forbidden) { var s = new HashSet<>(forbidden); int ans = 0, n = word.length(); for (int i = 0, j = 0; j < n; ++j) { for (int k = j; k > Math.max(j - 10, i - 1); --k) { if (s.contains(word.substring(k, j + 1))) { i = k + 1; break; } } ans = Math.max(ans, j - i + 1); } return ans; } }(code-box)

class Solution { public: int longestValidSubstring(string word, vector<string>& forbidden) { unordered_set<string> s(forbidden.begin(), forbidden.end()); int ans = 0, n = word.size(); for (int i = 0, j = 0; j < n; ++j) { for (int k = j; k > max(j - 10, i - 1); --k) { if (s.count(word.substr(k, j - k + 1))) { i = k + 1; break; } } ans = max(ans, j - i + 1); } return ans; } };(code-box)

func longestValidSubstring(word string, forbidden []string) (ans int) { s := map[string]bool{} for _, x := range forbidden { s[x] = true } n := len(word) for i, j := 0, 0; j < n; j++ { for k := j; k > max(j-10, i-1); k-- { if s[word[k:j+1]] { i = k + 1 break } } ans = max(ans, j-i+1) } return }(code-box)

function longestValidSubstring(word: string, forbidden: string[]): number { const s: Set<string> = new Set(forbidden); const n = word.length; let ans = 0; for (let i = 0, j = 0; j < n; ++j) { for (let k = j; k > Math.max(j - 10, i - 1); --k) { if (s.has(word.substring(k, j + 1))) { i = k + 1; break; } } ans = Math.max(ans, j - i + 1); } return ans; }(code-box)