LeetCode 3: Longest Substring Without Repeating Characters

最新推荐文章于 2021-12-03 15:58:56 发布

原创最新推荐文章于 2021-12-03 15:58:56 发布 · 328 阅读

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本文提供了一种高效的C++算法来解决寻找字符串中无重复字符的最长子串问题，通过实现一个类`Solution`，包含一个核心函数`lengthOfLongestSubstring`，该函数遍历字符串并利用数组`p_last_index`记录每个字符的最后出现位置，以此确定无重复字符子串的长度。

Difficulty: 3

Frequency: 2

Problem:

Given a string, find the length of the longest substring without repeating characters. For example, the longest substring without repeating letters for "abcabcbb" is "abc", which the length is 3. For "bbbbb" the longest substring is "b", with the length of 1.

Solution:

class Solution {
public:
    int lengthOfLongestSubstring(string s) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        int i_max_length = 0, i_max_length_from_end = 0;
        int p_last_index[26];
        memset(p_last_index, 0xFF, sizeof(int)*26);
        for (int i = 0; i<s.size(); i++)
        {
            if (p_last_index[s[i]-'a']==-1||(i-p_last_index[s[i]-'a'])>i_max_length_from_end)
            {
                p_last_index[s[i]-'a'] = i;
                i_max_length_from_end++;
                i_max_length = i_max_length>i_max_length_from_end?i_max_length:i_max_length_from_end;
            }
            else
            {
                i_max_length_from_end = i - p_last_index[s[i]-'a'];
                p_last_index[s[i]-'a'] = i;
            }   
        }
        return i_max_length;
    }
};

Notes:

Time complexity O(n).