How to write a program to remove all duplicate characters in a string?

#include

#include

int main()

{

            char str[100];

            int i, j, k;

            printf("\n Please Enter any String :  ");

            gets(str);                    

            for(i = 0; i < strlen(str); i++)

            {

                        for(j = i + 1; str[j] != '\0'; j++)

                        {

                                    if(str[j] == str[i]) 

                                    {

                                                for(k = j; str[k] != '\0'; k++)

                                                {

                                                            str[k] = str[k + 1];

                                                }

                                    }

                        }

            }          

            printf("\n The Final String after Removing All Duplicates = %s ", str);

            return 0;

}