[leetcode] Longest Substring Without Repeating Characters

標籤：class   blog   code   java   http   tar   

Given a string, find the length of the longest substring without repeating characters. For example, the longest substring without repeating letters for "abcabcbb" is "abc", which the length is 3. For "bbbbb" the longest substring is "b", with the length of 1.

https://oj.leetcode.com/problems/longest-substring-without-repeating-characters/

 

思路：利用一個exist數組儲存字元是否出現（假設char set是ascii），從前向後遍曆數組，如果遇到已存在的字元，應該回退到這個字元上次出現的下一個位置從新開始統計（如），同時注意exist數組的同步更新。

 

public class Solution {    public int lengthOfLongestSubstring(String s) {        if (s == null || s.length() == 0)            return 0;        int res = 1;        boolean[] exist = new boolean[256];        int start = 0;        for (int i = 0; i < s.length(); i++) {            char ch = s.charAt(i);            if (exist[ch]) {                res = Math.max(res, i - start);                for (int k = start; k < i; k++) {                    if (s.charAt(k) == ch) {                        start = k + 1;                        break;                    }                    exist[s.charAt(k)] = false;                }            } else                exist[ch] = true;        }        res = Math.max(res, s.length() - start);        return res;    }    public static void main(String[] args) {        System.out.println(new Solution().lengthOfLongestSubstring("abcabcbb"));        System.out.println(new Solution().lengthOfLongestSubstring("bbbbb"));        System.out.println(new Solution()                .lengthOfLongestSubstring("fpdcztbudxfipowpnamsrfgexjlbjrfoglthewbhtiriznzmolehqnlpwxrfowwwjrd"));    }}

 

 

 

參考：

http://blog.csdn.net/likecool21/article/details/10858799

http://www.programcreek.com/2013/02/leetcode-longest-substring-without-repeating-characters-java/