LeetCode "Longest Substring with At Most K Distinct Characters"

最新推荐文章于 2024-09-26 12:09:32 发布

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最新推荐文章于 2024-09-26 12:09:32 发布

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原文链接：http://www.cnblogs.com/tonix/p/5351320.html

本文介绍了一个简单的滑动窗口算法，用于寻找字符串中包含最多两个不同字符的最长子串。通过使用哈希表来跟踪字符出现次数，实现高效的查找过程。

A simple variation to "Longest Substring with At Most Two Distinct Characters". A typical sliding window problem.

class Solution {
public:
    int lengthOfLongestSubstringKDistinct(string s, int k) {
        unordered_map<char, unsigned> hm;
        
        int ret = 0, start = 0;
        for (int i = 0; i < s.length(); i++)
        {
            hm[s[i]]++;

            if (hm.size() <= k)
            {
                ret = std::max(ret, i - start + 1);
            }
            else
            {
                while (start < i && hm.size() > k)
                {
                    char nc = s[start];
                    if (hm[nc] == 1)    hm.erase(nc);
                    else                hm[nc]--;
                    
                    start++;
                }
            }
        }
        return ret;
    }
};