共计 931 个字符，预计需要花费 3 分钟才能阅读完成。
Given a string, find the length of the longest substring without repeating characters.
Example 1:
Input: “abcabcbb”Output: 3 Explanation: The answer is “abc”, with the length of 3. Example 2:
Input: “bbbbb”Output: 1Explanation: The answer is “b”, with the length of 1.Example 3:
Input: “pwwkew”Output: 3Explanation: 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.
难度：medium
题目：给定一字符串，找出最长且无重复字符的子串。
思路：
创建字符下标数组用以记录访问过的字符串中的字符。下标由 1 开始，用以区别数组的初始化值 0.
定义子串的起始下标，子串的窗口为 [begin indx, i]
Runtime: 19 ms, faster than 96.64% of Java online submissions for Longest Substring Without Repeating Characters.
class Solution {
public int lengthOfLongestSubstring(String s) {
if (null == s || “” == s) {
return 0;
}
int[] charIdxArray = new int[256];
int maxLen = 0;
int beginIdx = 0;
for (int i = 0; i < s.length(); i++) {
char c = s.charAt(i);
int idx = charIdxArray;
if (idx < 1 || idx <= beginIdx) {
charIdxArray = i + 1;
} else {
beginIdx = idx;
charIdxArray = i + 1;
}
maxLen = Math.max(maxLen, i + 1 – beginIdx);
}
return maxLen;
}
}
