leetcode 3. Longest Substring Without Repeating Characters

int lengthOfLongestSubstring(string s) {

if(s == ""){

return 0;

}else if(s.length() == 1){

return 1;

}

int i=0,length=0;

int SumLength=0;

bool isExist[256] = {false};

int flag=0;

while(i< s.length()){

if(isExist[s[i]] == false){

isExist[s[i]] = true;

length++;

if(i == s.length()-1){

if(SumLength < length)

{

SumLength =length;

}

}

i++;

}else{

if(SumLength < length){

SumLength =length;

}

for(int j=i-length;j<i;j++){

isExist[s[j]] = false;

}

i=i-length+1;

length=0;

}

}

return SumLength;

}