[LeetCode] Longest Substring Without Repeating Characters

#if 0
class Solution {
public:
    int lengthOfLongestSubstring(string s) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        int locs[256];//保存字符上一次出现的位置
        memset(locs, -1, sizeof(locs));

        int idx = -1, max = 0;//idx为当前子串的开始位置-1
        for (int i = 0; i < s.size(); i++)
        {
            if (locs[s[i]] > idx)//如果当前字符出现过，那么当前子串的起始位置为这个字符上一次出现的位置+1
            {
                idx = locs[s[i]];
            }

            if (i - idx > max)
            {
                max = i - idx;
            }

            locs[s[i]] = i;
        }
        return max;
    }
};
#endif
class Solution 
{
    public:   
        int lengthOfLongestSubstring(string s)  
        {   
            int hash[256]; // save the index of s[i]
            int  start = -1; 
            int len = 0;

            memset(hash, -1, sizeof(hash));

            for(int i = 0; i< s.size(); i++/**/)
            {   
                // update the start if the start is in the front of the old hash[s[i]]
                if(start < hash[s[i]])
                    start = hash[s[i]];
                len = max(i - start, len);
                hash[s[i]] = i;
            }   

            return len;
        }   
};