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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.
问题：求字符串不含重复字符的最长子字符串（注意子字符串是连续的，子序列可以不用连续，上面第三条例子）
思路：不含重复字符的最长子字符串，即为两个重复字符之间的子字符串中最长的一个（或者全部字符，整个字符串没有重复字符）。
代码如下：（参考九章算法http://www.jiuzhang.com/solutions/longest-substring-without-repeating-characters/）
1 class Solution { 2 public: 3 int lengthOfLongestSubstring(string s) { 4 // 题意为求不包含重复字符的最长子串 5 // left用以记录合法的最远左边界位置，last记录字符上一次出现的位置 6 int ans = 0, left = 0, len = s.length(); 7 int last[255]; 8 memset(last, -1, sizeof last); 9 10 for (int i = 0; i < len; i++) { 11 // 上次出现位置在当前记录边界之后，即该子串中出现了重复字符，需调整left使得子串合法 12 if (last[s[i]] >= left) left = last[s[i]] + 1; 13 last[s[i]] = i; 14 ans = max(ans, i - left + 1); 15 } 16 return ans; 17 } 18 };
LeetCode 3.Longest Substring Without Repeating Characters
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原文地址：http://www.cnblogs.com/gexinmen/p/5932311.html
