Q3：Longest Substring Without Repeating Characters

3. Longest Substring Without Repeating Characters

官方的链接：3. Longest Substring Without Repeating Characters

Description ：

Given a string, find the length of the longest substring without repeating characters.

Example:

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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.

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问题描述

 给定一个字符串，找出最长不重复子串的长度

思路

 建立一个128的数组，存储字符的下标，min存储非重复子串的最小下标，max存储最大下标。max逐步加大，如果下一个字符的下标大于min，则增加min，同时记录最大的max - min + 1

[github-here]

 

public class Q3_LongestSubstringWithoutRepeatingCharacters {
    public int lengthOfLongestSubstring(String s) {
        if (null == s || s.length() < 1) {
            return 0;
        }
        // 初始化128的数组，足够存储所有字符
        int[] intArray = new int[128];
        for (int i = 0; i < intArray.length; i++) {
            intArray[i] = -1;
        }
        char num = s.charAt(0);
        intArray[num] = 0;
        int min = 0;
        int max = 0;
        int count = 1;
        for (int i = 1; i < s.length(); i++) {
            num = s.charAt(i);
            max = i;
            if (intArray[num] == (max - 1)) {
                count = max - min > count ? max - min : count;
                min = max;
            } else if (intArray[num] >= min) {
                count = max - intArray[num] > count ? max - intArray[num] : count;
                min = intArray[num] + 1;
            } else {
                count = max - min + 1 > count ? max - min + 1 : count;
            }
            intArray[num] = i;
        }
        return count;
    }

    public static void main(String[] args) {
        Q3_LongestSubstringWithoutRepeatingCharacters longest = new Q3_LongestSubstringWithoutRepeatingCharacters();
        System.out.println(longest.lengthOfLongestSubstring("nfpdmpi"));
    }
}