Longest Substring Without Repeating Characters

时间 2019-11-12

标签 longest substring repeating characters 繁體版

原文原文链接

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. java

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

思路：利用一个exist数组保存字符是否出现（假设char set是ascii），从前向后遍历数组，若是遇到已存在的字符，应该回退到这个字符上次出现的下一个位置重新开始统计（以下图），同时注意exist数组的同步更新。 .net

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"));

    }
}

参考： code

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

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