How to print part of words in string by input using array in c?

Question

The C program below print the third until last character of 80 words strings

#include <stdio.h>

int main(void) {
  char a[] = "computer";
  char start = 3;
  char length = 7;

  printf("%.*s\n", length, a + start);

  return 0;
}

the output :

puter

how to write in c code for print "n" last character of string

ex:

• string : "this computer"

• n inputed by scanf ex: 5

it will print to console

"puter"

Answer 1

Change

char start = 3;
char length = 7;

to

int start;
int length;

and do as follows; I used a pointer in this program.

#include <stdio.h>
#include <string.h>

int main(void) {
    char a[] = "this computer";
    int start;
    int length;
    char *ptr = a; // Initializing ptr with first element of string literal.

    length = strlen(a); // Calculating the length of string literal
    scanf("%d", &start);

    if(start > length)
        start = length;

    ptr += length - start; // Adding the desired last number of elements/characters to be printed to the address ptr points to. 

    printf("%s\n", ptr);

    return 0;
}

Input:

5  

Output:

puter

Answer 2

In case the string, of which you're trying to print a substring is not hard-coded, you'll need to determine its length, too:

char some_string[] = "this computer";
char *out_ptr = &some_string;
int length, offset;
length = strlen(some_string);
scanf("%d", &offset);
out_ptr += length - offset;
printf("%s", out_ptr);

This allows you to pour this into a neat little function:

void print_substr(char *str_ptr)
{
    int offset, len = strlen(str_ptr);
    scanf("%d", &offset);
    if (offset > len) offset = len;
    str_ptr += len - offset;
    printf("%s\n", str_ptr);
}

And it's dead-easy to use, as you can see here, on this code-pad

Answer 3

Here's how I would do it:

void print_substring(const char *string, unsigned int start, unsigned int length)
{
  const size_t len = strlen(string);

  if(start >= len)
    return;
  if(start + length > len)
    length = len - start;
  for(; length != 0; --length)
    putchar(string[start++]);
  putchar('\n');
}

Answer 4

 #include <stdio.h>

int main(void) {
  char a[] = "computer";
  char start = 3;
  char length = 8;
  int n;
  scanf("%d",&n);
  printf("%.*s\n", n,&a[length-n]);

  return 0;
}