Given a string, find the length of the longest substring T that contains at most k distinct characters.
For example, Given s = “eceba” and k = 2, T is "ece" which its length is 3.
int lengthOfLongestSubstringKDistinct(string s, int k){
if(k == 0 || s.length() == 0) return 0;
vector<int> dict(256, 0);
int count = 0, maxLength = 0, start = 0;
for(int i = 0; i < s.length(); i++){
dict[s[i]]++;
if(i == 0 || s[i] == s[i-1] || count < k) {
if(dict[s[i]] == 1) count++;
continue;
}
// k+1 distinctive char
if((count == k && dict[s[i]] == 1)){
maxLength = max(maxLength,i-start);
while(start <= i){
dict[s[start]]--;
if(dict[s[start]] == 0) break;
start++;
}
start++;
}
}
return maxLength > (s.length() - start) ? maxLength : s.length() - start;
}
