Find longest substring without repeating characters

Question

Given a string S of length N find longest substring without repeating characters.

Example:

Input:

Answer 1

I am posting O(n^2) in python . I just want to know whether the technique mentioned by Karoly Horvath has any steps that are similar to existing search/sort algorithms ?

My code :

def main():
    test='stackoverflow'
    tempstr=''
    maxlen,index=0,0
    indexsubstring=''
    print 'Original string is =%s\n\n' %test

    while(index!=len(test)):
        for char in test[index:]:
            if char not in tempstr:
                tempstr+=char
                if len(tempstr)> len(indexsubstring):
                   indexsubstring=tempstr
            elif (len(tempstr)>=maxlen):
                   maxlen=len(tempstr)
                   indexsubstring=tempstr
                   break
        tempstr=''
        print 'max substring length till iteration with starting index =%s is %s'%(test[index],indexsubstring)
        index+=1

if __name__=='__main__':
    main()