Find words in a string with characters that are repeated - c++

Question

I was given the task to remove all extra spaces (should remain 1) and output only those words in which the letters are repeated. I've been sitting for a week and can't find the error, maybe this will help me)))
I've figured out the whitespace, but the word formatting I can't do((
Please help me find a bug in my code
If I enter I like to play soccer every day, the program should output soccer every.
#include <iostream>
#include <stdio.h>
#include <stdlib.h>
using namespace std;
int main()
{
char str[128];
printf("Write String: ");
fgets(str, 128, stdin);
int i = 0, j;
i = 0;
int start = i;
while (str[i] != '\0')
{
if (str[i] == ' ' || str[i] == '\n')
{
int end = i;
int first = start;
int first2 = start + 1;
int last = end - 1;
while (first < last)
{
for (first; first < last; first++)
{
for (first2; first2 < last; first2++)
{
if ((str[first] == str[first2]) && (first != first2))
{
break;
}
else
{
if((first == last - 1) && (first2 == last - 1))
{
for (j = start; str[end] != '\0'; ++end)
{
str[j] = str[end + 1];
j += 1;
}
}
}
}
}
}
if (i != start)
{
start = i + 1;
++i;
}
}
else
{
++i;
}
}
}

Answer 1

A possible solution:
read your input one word at a time, and
check if each word has a repeated letter. If it does, print the word.
Now, how to read the input one word at a time. In the example below I've used a std::istringstream, but std::cin would do.
And, how to check if a word has a repeated letter. A simple, surely not the fastest, way is to create a set from an input string, and check if the set and the string don't have the same number of letters. I've used a lambda for has_a_repeated_letter but a function would do.
[Demo]
#include <iostream> // cout
#include <set>
#include <string>
#include <sstream> // istringstream
int main() {
std::istringstream iss{"I like to play soccer every day"};
auto has_a_repeated_letter = [](const std::string& word) {
std::set<char> letters{ word.begin(), word.end() };
return letters.size() != word.size();
};
std::string word{};
while (iss >> word) {
if (has_a_repeated_letter(word)) {
std::cout << word << " ";
}
}
}
// Outputs:
//
// soccer every