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.
给定一个字符串，返回其最大不重复长度。

解法如下(字符重复时，重复位置之前的字符可以不用遍历 既i=k)：

func lengthOfLongestSubstring(s string) int {
    length := 0
    if len(s) > 0 {
        length = 1
    }
    bs := []byte(s)
    for i := 0; i < len(bs); i++ {
        flag := 0
        for j := i + 1; j < len(bs); j++ {
            for k := i; k < j; k++ {
                if bs[k] == bs[j] {
                    flag = 1
                    break
                }
            }
            if flag > 0 {
                break
            }
            if j-i+1 > length {
                length = j - i + 1
            }
        }
    }
    return length
}