LeetCode Algorithm 0003 - Longest Substring Without Repeating Characters (Medium)

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LeetCode Algorithm 0003 - Longest Substring Without Repeating Characters (Medium)

Problem Link: https://leetcode.com/problems/longest-substring-without-repeating-characters/description/

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Description

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

Example 1:

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

Example 2:

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

Example 3:

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

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Solution C++

#pragma once

#include "pch.h"

// Problem: https://leetcode.com/problems/longest-substring-without-repeating-characters/description/

namespace P3LongestSubstringWithoutRepeatingCharacters
{
    class Solution
    {
        public:
        int lengthOfLongestSubstring(string s)
        {
            unordered_map<char, size_t> char2Index;

            int maxLen = 0;
            int next = 0;

            for (size_t i = 0; i < s.size(); i++)
            {
                if (char2Index.find(s[i]) != char2Index.end())
                {
                    if (next < char2Index[s[i]] + 1)
                    {
                        next = char2Index[s[i]] + 1;
                    }
                }

                char2Index[s[i]] = i;

                if (maxLen < i - next + 1)
                {
                    maxLen = i - next + 1;
                }
            }

            return maxLen;
        }
    };
}

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