Read a char array and modify it

Question

So for this program the user gives a text and it must print the text back modifying in these ways by adding and removing space between words:

1. Each line should contain 60 characters and be aligned left and right
2. In each line the biggest space between two words must be bigger than the smallest by only one character and a bigger space must be righter than a smaller one. This is what I have managed to do yet, but without any success.

I tried C++ strings instead of a char array but my knowledge about them is limited yet.

#include <iostream>
using namespace std;

bool isletter(char c) {
  return c >= 'a' and c <= 'z' or c >= 'A' and c <= 'Z';
}

int main() {
  int c, i = 0, constant = 0, counter = 0;
  char text[1500], original[1500];

  do {
    c = getchar();
    original[i] = c;
    i++;
  } while (c != EOF);

  for (int j = 0; j <= i; j++) {
    if (original[j] == ' ') {
      int n = 0;
      j = constant;
      while (not isletter(original[j])) {
        n++;
        text[constant] = original[j];
        j = j + n;
      }
      counter++;
    } else if (text[j] == '\n') {
      text[j] = ' ';
      counter++;
    } else {
      text[j] = original[j];
      counter++;
    }
  }
  for (int i = 0; i < counter; i++) {
    cout << text[i];
  }
}