Given a string, find the length of the longest substring without repeating characters.
Examples:
Given "abcabcbb", the answer is "abc", which the length is 3.
Given "bbbbb", the answer is "b", with the length of 1.
Given "pwwkew", the answer is "wke", with the length of 3. Note that the answer must be a substring, "pwke" is a subsequence and not a substring.
解题思路：maxLen代表当前已经找到的满足条件的最长子串的长度，两个int指针start和end，s[start]至s[end-1]表示当前已经遍历到的不含重复字符的子串，s[end]表示当前正在遍历的字符：
如果s[end]包含在s[start]至s[end-1]的子串中，那么找到与s[end]重复的那个字符的位置，将start移动到这个位置+1的位置，并将end++然后继续遍历;
如果不包含的话，那么这时候将end-start+1与maxLen比较，如果大于maxLen，那么替换maxLen。然后end++并继续遍历。
直到end的值超出字符串的长度范围。
解题代码：（53ms，beats 70.53%）
class Solution {
public int lengthOfLongestSubstring(String s) {
if (s.length() < 2) {
return s.length();
}
int maxLen = 1, start = 0, end = 1, len = 1;
String curStr;
while (end < s.length()) {
curStr = s.substring(start, end);
if (curStr.contains(String.valueOf(s.charAt(end)))) {
start = s.indexOf(s.charAt(end), start) + 1;
end++;
continue;
}
len = end - start + 1;
if (len > maxLen) {
maxLen = len;
}
end++;
}
return maxLen;
}
}