3. 无重复字符的最长子串

1.题意

给定一个字符串，请你找出其中不含有重复字符的 最长子串 的长度。
示例 1:

输入: s = “abcabcbb”
输出: 3
解释: 因为无重复字符的最长子串是 “abc”，所以其长度为 3。

2. 思路

这题应该没有好说的就是不重复最长子串，可二位做或者一维做

法一暴力

class Solution {
public:
    int lengthOfLongestSubstring(string s) {
        int n = s.size();
        int mp[256];
        memset(mp, 0, sizeof(mp));
        int num = 0, re = 0, index = 0;
        for(int i = 0; i < n; i++){
            if(mp[s[i]]){
                index = max(index, mp[s[i]]);
                // cout<<num<<" "<<i<<"  "<<mp[s[i]]<<endl;
                re = max(re, num), num = i - index + 1;
                mp[s[i]] = i + 1;
                // cout<<num<<" ";
                continue;
            }
            num++, mp[s[i]] = i + 1;

        }
        re = max(re, num);
        return re;
    }
};

法二滑动窗口优化

言： cpp


class Solution {
public:
    int lengthOfLongestSubstring(string s) {
        int n = s.size();
        int mp[256];
        memset(mp, 0, sizeof(mp));
        int num = 0, re = 0, index = 0;
        for(int i = 0; i < n; i++){
            if(mp[s[i]]){
                index = max(index, mp[s[i]]);
                // cout<<num<<" "<<i<<"  "<<mp[s[i]]<<endl;
                re = max(re, num), num = i - index + 1;
                mp[s[i]] = i + 1;
                // cout<<num<<" ";
                continue;
            }
            num++, mp[s[i]] = i + 1;

        }
        re = max(re, num);
        return re;
    }
};