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# Longest Substring Without Repeating Characters

## 原文

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.

## Code 1（C++）

class Solution {
public:
int lengthOfLongestSubstring(string s) {
int len = s.Length;
int head = 0, index = 0, maxLen = 0;
bool[] exist = new bool[256];
for (int i = 0; i < exist.Length; i++)
exist[i] = false;
while (index < len){
if (exist[s[index]]){
maxLen = Math.Max(maxLen, index - head);
}
}
else{
exist[s[index]] = true;
index++;
}
}
maxLen = Math.Max(maxLen, len - head);
return maxLen;
}
};

## Code 1 C

public class Solution
{
public int LengthOfLongestSubstring(string s)
{
int len = s.Length;
int head = 0, index = 0, maxLen = 0;
bool[] exist = new bool[256];
for (int i = 0; i < exist.Length; i++)
exist[i] = false;
while (index < len)
{
if (exist[s[index]])
{
maxLen = Math.Max(maxLen, index - head);
{
}
}
else
{
exist[s[index]] = true;
index++;
}
}
maxLen = Math.Max(maxLen, len - head);
return maxLen;
}
}

## Code 1 Java

public class Solution {
public int lengthOfLongestSubstring(String s) {
int len=s.length();
boolean[] exist=new boolean[256];
for(boolean e : exist)
e=false;
while(index<len){
if(exist[s.charAt(index)]){
}
}
else{
exist[s.charAt(index)]=true;
index++;
}
}
}
}

## Code 2 C++


static  int lengthOfLongestSubstring(string s)
{
int ascii[256];
for(int i=0; i<256; i++) ascii[i] = -1;
int start = 0, ans = 0;
int i;
for(i=0; i<s.size(); i++){
if( -1 != ascii[ s[i] ] ){
if(ans < i-start) ans = i-start;
for(int j=start; j<ascii[ s[i] ]; j++)
ascii[j] = -1;
if(ascii[s[i]] + 1 > start )
start = ascii[s[i]] +1;
}
ascii[s[i]] = i;
}
if(ans < i-start) ans = i-start;
return ans;
}
　`