[LeetCode]Longest Substring Without Repeating Characters

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.

 

LeetCode水题,无聊水一发,题目是求最长不重复字符的子字符串.

Ok,that's right.

简单分析下:

1.当不发生重复字符出现时,直接加入到集合.

2.当发生重复字符的时候,先记录下当前集合的长度,取current.size() > maxLength;maxLength = current.size(),然后要把发生重复的字符前面的序列去掉,并且吧新的字符加入到集合.

(exp:cdvdfa,当道第二个d时,需要把cd去掉,形成vdfa序列即可).

3.重复1 2.

 

JAVA CODE:

    public int lengthOfLongestSubstring( String s ) {
        int maxLength = 0;
        List<Character> exist = new ArrayList<Character>();

        for( int i = 0; i < s.length(); i++ ) {
            if( !exist.contains( s.charAt( i ) ) ) {
                exist.add( s.charAt( i ) );
            } else {
                if( exist.size() > maxLength ) {
                    maxLength = exist.size();
                }
                while( !exist.isEmpty() && exist.get( 0 ) != s.charAt( i ) ) {
                    exist.remove( 0 );
                }
                exist.remove( 0 );
                exist.add( s.charAt( i ) );
            }
        }
        if( exist.size() > maxLength )
            maxLength = exist.size();
        return maxLength;
    }