Longest Distinct characters in string

PROBLEM :

Given a string, find length of the longest substring with all distinct characters.  For example, for input "abca", the output is 3 as "abc" is the longest substring with all distinct characters.

Input:

The first line of input contains an integer T denoting the number of test cases.
The first line of each test case is String str.

Output:

Print length of smallest substring with maximum number of distinct characters.
Note: The output substring should have all distinct characters.

Constraints:

1 = T = 100
1 = size of str = 10000

Example:

Input
2
abababcdefababcdab
geeksforgeeks

Output:
6
7

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SIMPLE c++ IMPLEMENTATION :(Using Auxilary arry)
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#include<iostream>
using namespace std;
#include<string.h>
int Longest_Distinct_characters_string(string ) ;
int main()
 {
int t,ans ;
string str ;
cin>>t ;
while(t--)
{
   cin>>str ;
   ans=Longest_Distinct_characters_string(str) ;
 
   cout<<ans<<endl ;
}
return 0;
}

int Longest_Distinct_characters_string(string str)
{
    int l,i,j,count,max ;
    l=str.length() ;
    max=0 ;
   
    for(i=0;i<l;i++)
    {
        int hash[256]={0} ;
        count=0 ;
        for(j=i;j<l;j++)
        {
            if(hash[str[j]]==0)
            {
                hash[str[j]]++ ;
                count++ ;
            }
            else
                break ;
        }
        if(max<count)
            max=count ;
    }
    return max ;
}

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