Longest Substring Without Repeating Characters LeetCode Solution

Problem – Longest Substring Without Repeating Characters LeetCode Solution

Given a string s, find the length of the longest substring without repeating characters.

Example 1:

Input: s = "abcabcbb"
Output: 3
Explanation: The answer is "abc", with the length of 3.

Example 2:

Input: s = "bbbbb"
Output: 1
Explanation: The answer is "b", with the length of 1.

Example 3:

Input: s = "pwwkew"
Output: 3
Explanation: The answer is "wke", with the length of 3.
Notice that the answer must be a substring, "pwke" is a subsequence and not a substring.

Constraints:

• 0 <= s.length <= 5 * 104
• s consists of English letters, digits, symbols and spaces.

Longest Substring Without Repeating Characters LeetCode Solution in Java

   public int lengthOfLongestSubstring(String s) {
        if (s.length()==0) return 0;
        HashMap<Character, Integer> map = new HashMap<Character, Integer>();
        int max=0;
        for (int i=0, j=0; i<s.length(); ++i){
            if (map.containsKey(s.charAt(i))){
                j = Math.max(j,map.get(s.charAt(i))+1);
            }
            map.put(s.charAt(i),i);
            max = Math.max(max,i-j+1);
        }
        return max;
    }

Longest Substring Without Repeating Characters LeetCode Solution in C++

int lengthOfLongestSubstring(string s) {
        vector<int> dict(256, -1);
        int maxLen = 0, start = -1;
        for (int i = 0; i != s.length(); i++) {
            if (dict[s[i]] > start)
                start = dict[s[i]];
            dict[s[i]] = i;
            maxLen = max(maxLen, i - start);
        }
        return maxLen;
    }

Longest Substring Without Repeating Characters LeetCode Solution in Python

class Solution:
    # @return an integer
    def lengthOfLongestSubstring(self, s):
        start = maxLength = 0
        usedChar = {}
        
        for i in range(len(s)):
            if s[i] in usedChar and start <= usedChar[s[i]]:
                start = usedChar[s[i]] + 1
            else:
                maxLength = max(maxLength, i - start + 1)

            usedChar[s[i]] = i

        return maxLength

Longest Substring Without Repeating Characters LeetCode Solution in JavaScript

function lengthOfLongestSubstring(s) {
    const map = {};
    var left = 0;
    
    return s.split('').reduce((max, v, i) => {
        left = map[v] >= left ? map[v] + 1 : left;
        map[v] = i;
        return Math.max(max, i - left + 1);
    }, 0);
}

Longest Substring Without Repeating Characters LeetCode Solution in Swift

class Solution {
    func lengthOfLongestSubstring(_ s: String) -> Int {
        guard !s.isEmpty else { return 0 }
        var len = 0, chars: [Character] = []
        for c in s {
            if let idx = chars.firstIndex(of: c) {
                chars.removeSubrange(0...idx)
            }
            chars.append(c)
            len = max(len, chars.count)
        }
        return len
    }
}

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