determine if a string has all unique characters?

Question

Can anybody tell me how to implement a program to check a string contains all unique chars ?

Answer 1

Without using additional memory:

#define UNIQUE_ARRAY 1
int isUniqueArray(char* string){
    if(NULL == string ) return ! UNIQUE_ARRAY;
    char* current = string;
    while(*current){
        char* next   = current+1;
        while(*next){
            if(*next == *current){
                return ! UNIQUE_ARRAY;
            }
            next++;
        }
        current++;
    }
    return UNIQUE_ARRAY;
}