leetcode-3-字符串题-无重复字符的最长字串

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题目

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解法

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// 滑动窗口
class Solution {
public:
    int lengthOfLongestSubstring(string s) {
        int n = s.size();
        if(s.empty()) return 0;
        if(n == 1) return 1;

        unordered_map<char, int> charIndex;
        int maxLen = 0;

        for(int i = 0, j = 0; j < n; ++j){
            if(charIndex.count(s[j]) > 0){
                i = max(i, charIndex[s[j]]);
                charIndex[s[j]] = j+1;
            }else{
                charIndex.insert({s[j], j+1});
            }
            maxLen = max(maxLen, j-i+1);
        }

        return maxLen;
    }
}；

// 动态规划
class Solution {
public:
    int lengthOfLongestSubstring(string s) {
        int n = s.size();
        if(s.empty()) return 0;
        if(n == 1) return 1;

        unordered_map<char, int> charIndex;
        int curLen = 0;
        int maxLen = 0;

        for(int i = 0; i < n; ++i){
            if(charIndex.count(s[i]) > 0){
                if(i - charIndex[s[i]] > curLen){
                    ++curLen;
                }else{
                    if(curLen > maxLen) maxLen = curLen;
                    curLen = i - charIndex[s[i]];
                }
                charIndex[s[i]] = i;
            }else{
                ++curLen;
                charIndex.insert({s[i], i});
            }
        }
        if(curLen > maxLen) maxLen = curLen;
        return maxLen;
    }
};