[LeetCode]Longest Substring Without Repeating Characters

class Solution {
public:
int lengthOfLongestSubstring(string s) {
int start = 0; // current start point of substring without dup
int maxlen = 0; // max length of substring found
int table[256]; // hash table for index of each char appeared
for (int i = 0;i < 256;i++) table[i] = -1; // if char not present, index is -1
for (int i = 0;i < s.length();i++) {
if (table[s[i]] != -1) {
while (start <= table[s[i]]) table[s[start++]] = -1;
}
if (i - start + 1 > maxlen) maxlen = i - start + 1;
table[s[i]] = i;
}
return maxlen;
}
};