第三题

#include <algorithm>
using namespace std;
char seti[256];
class Solution {
public:
    int lengthOfLongestSubstring(string s) {
        int res = 0;
        int size = s.size();
        for(int i = 0; i < size; i++){
            memset(seti, 0, sizeof(seti));
            int temp = 1;
            seti[s[i]] = 1;
            int j = i + 1;
            while(j != size && seti[s[j]] == 0){
                seti[s[j]] = 1;
                j++;
                temp++;
            }
            if(j == size){
                res = max(res,temp);
                return res;
            }
            res = max(res,temp);
        }
        return res;
    }
};

#include <algorithm>
#include <vector>
using std::max;
using std::vector;

class Solution {
public:
    int lengthOfLongestSubstring(string s) {
        static const int DICT_SIZE = 256;
        
        int ls = s.size();
        if (ls < 2) {
            return ls;
        }
        
        vector<int> c(DICT_SIZE, 0);
        int i, j;
        int res = 0;
        j = 0;
        for (i = 0; i < ls; ++i) {
            ++c[s[i]];
            if (c[s[i]] > 1) {
                while (c[s[i]] > 1) {
                    --c[s[j++]];
                }
            }
            res = max(res, i - j + 1);
        }
        c.clear();
        return res;
    }
};