Longest Substring Without Repeating Characters

翻譯

給定一個(gè)字符串，找出其沒(méi)有重復(fù)字符的最大子序列的長(zhǎng)度?！　?例如，“abcabcbb”的無(wú)重復(fù)字符的最大子序列是“abc”，它的長(zhǎng)度是　3。　　 “bbbbb”的最大子序列是“b”，它的長(zhǎng)度是　1。

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);
                 while (s[head] != s[index]){
                     exist[s[head]] = false;
                     head++;
                 }
                 head++; index++;
             }
             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);
                while (s[head] != s[index])
                {
                    exist[s[head]] = false;
                    head++;
                }
                head++; index++;
            }
            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();
        int head=0,index=0,maxLen=0;
        boolean[] exist=new boolean[256];
        for(boolean e : exist)
            e=false;
        while(index<len){
            if(exist[s.charAt(index)]){
                maxLen=Math.max(maxLen, index-head);
                while(s.charAt(head)!=s.charAt(index)){
                    exist[s.charAt(head)]=false;
                    head++;
                }
                head++; index++;
            }
            else{
                exist[s.charAt(index)]=true;
                index++;
            }
        }
        return maxLen= Math.max(maxLen,len-head);
    }
}

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;
}
```