It's not printing the new array. What could be the reason?

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#include <stdio.h>
char q[50];
int doo(int p, int n, char* s) {
  int i = 0, j = 0;
  while (s[i] != '\0') {
    if ((i < p) && (i > (p + n))) {
      q[j] = s[i];
      ++j;
    }
    i++;
  }
  puts(p);
}
int main() {
  char s[50];
  int n, p;
  printf("<--program by gautam-->\n");
  printf("enter the string-->");
  gets(s);
  printf("\nenter the numbers of character to be deleted and position-->");
  scanf("%d%d", &n, &p);
  --p;
  doo(p, n, s);
  return 0;
}

The task is to delete certain elements of a string by asking the user the position and number of elements to delete. I'm trying to copy all elements except those whose position is provided by user, but I'm getting no output at all.

c
1 Answers

The fundamental error in your code is that you are using the && operator in the test inside your while loop, whereas you should be using the || operator: if either of the conditions is true, then add the character to the output string.

Also, your doo function is declared as returning an int but it doesn't return anything: I fixed this in the code below by returning j (the count of characters copied) but, as you never use that, you may want to redeclare the function as void, instead.

You are also attempting to print p with the puts function, where you most likely want to print q (I can put this one down to a typo).

Lastly: Never use the gets function! Why is the gets function so dangerous that it should not be used? Use fgets(), instead - it's much safer, as it will never read in more characters than you tell it to, so the buffer won't overflow (if you specify the correct size).

Here's a 'fixed' version of your code, with comments added where I've made changes:

#include <stdio.h>
char q[50];

int doo(int p, int n, char* s)
{
    int i = 0, j = 0;
    while (s[i] != '\0') {
        if ((i < p) || (i > (p + n))) { // Need OR not AND here
            q[j] = s[i];
            ++j;
        }
        i++;
    }
    q[j] = '\0'; // Add nul terminator (don't need if only calling once, but best to have it anyway)
    puts(q); // Should be printing "q" (result string) NOT "p" (position).
    return j; // MUST return something - here, the count of characters
}

int main()
{
    char s[50];
    int n, p;
    printf("<--program by gautam-->\n");
    printf("enter the string-->");
    fgets(s, 50, stdin); // NEVER use gets - it's been removed from the language!
    printf("\nenter the numbers of character to be deleted and position-->");
    scanf("%d%d", &n, &p);
    --p;
    doo(p, n, s);
    return 0;
}
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