3. Longest Substring Without Repeating Characters

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最新推荐文章于 2025-05-18 01:04:12 发布

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分类专栏： LeetCode 文章标签：无重复字符的最长子串 map 双指针

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本文介绍了一种求解字符串中无重复字符的最长子串长度的算法，通过使用哈希表和双指针技术，有效地解决了这一问题，并提供了详细的代码实现。

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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.

已知一个字符串，求用该字符串的无重复字符的最长子串的长度。

解决方案：使用哈希表统计字符出现的次数，使用双指针维护一个字符窗口，满足窗口内的字符不重复。统计最长的无重复字符子串。

class Solution {
public:
    int lengthOfLongestSubstring(string s) {
       if (s.size() == 0)
			return 0;
		int begin = 0, i = 0;
		map<char, int> log;
		int maxLen = 0;
		while(i<s.size())
		{
			int len;
			if (log.find(s[i]) != log.end())
			{
				int pos = log[s[i]] + 1;
				for (int j = begin; j < pos; j++)
				{
					log.erase(s[j]);
				}	
				begin = pos;
			}
			log[s[i]] = i;					
			len = i - begin +1;
			i++;
			if (len > maxLen)
				maxLen = len;
		}
		return maxLen;
    }
};