Member Avatar for mmcshmi11

I need to print out a number that begins with 7, without the seven. For example, print 71011 as 1011 or 701 as 01. I've tried many techniques and just can't get it to work. Is there a printf format that will let me print out everything left of the decimal minus that very left number? I've also tried to make a string that will contain the 0's and 1's, but not the 7... it is not working however.

Any help would be greatly appreciated. Thanks

  • 4 Contributors
  • 7 Replies
  • 127 Views
  • 1 Day Discussion Span
  • Latest Post Latest Post by invisal

Dani AI

Generated

A quick summary and two robust options, building on what , and started. 's idea of converting to text and skipping the first character is the simplest when you control formatting. 's remainder approach can work but you must compute the correct power-of-10 and it breaks if you need to preserve leading zeros. 's loop prints digits in reverse unless you buffer them first.

String-first (recommended when leading zeros matter or input is textual). Read or format the value into a string, handle an optional sign, then remove the first digit if it is '7'. Using memmove avoids manual copying and keeps the trailing nul:

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

void strip_first7_from_input(void)
{
    char buf[64];
    if (!fgets(buf, sizeof buf, stdin)) return;      /* or use snprintf(buf,...) */
    size_t len = strlen(buf);
    if (len && buf[len-1] == '\n') buf[--len] = '\0';
    char *start = buf + (buf[0] == '-' ? 1 : 0);     /* preserve sign */
    if (start[0] == '7') memmove(start, start + 1, strlen(start));
    fputs(buf, stdout);
    putchar('\n');
}

Numeric approach (when working purely with integers and you know they fit in your integer type). Use log10/pow to compute the highest power of ten and take the remainder; this avoids hard-coded masks or guessing digit counts:

#include <math.h>

long long drop_msd(long long v)
{
    if (v < 0) return -drop_msd(-v);
    if (v < 10) return v;
    int expo = (int)floor(log10((double)v));
    long long mask = (long long)pow(10.0, expo);
    return v % mask;
}

Cautions: integer literals starting with 0 are octal in C (so 07011 is not decimal). Use snprintf rather than sprintf to avoid buffer overflows. For very large values prefer long long or handle everything as strings. If exact digit counts or portability are critical prefer the string method — it is straightforward and preserves formatting (leading zeros, sign) without floating-point precision worries.

Recommended Answers

All 7 Replies

Member Avatar for Narue

Use sprintf to convert the number to a string and then print all but the first character:

sprintf ( buffer, "%d", value );
puts ( &buffer[1] );
Member Avatar for gerard4143

try the modulus operator %

ie

int x = (71011 % 70000);

and x = 1011

Member Avatar for mmcshmi11

Thanks for the help guys, I finally got it working with the sprintf tip. The modulus wont work if my number starts with 0 however, learned that the hard way already, but thanks for the help!

Member Avatar for Narue

>The modulus wont work if my number starts with 0
Your number won't start with 0 if you store it in an integer type. Leading zeros are ignored on formatted integer input and during integer processing. The only way to get the leading zero is to convert the number to a formatted string that specifies a field width and zero fill:

sprintf ( buffer, "%0*d", digits + 1, value );

The real problem with the remainder operator is that you're extracting the most significant digit, which involves finding the width of the number to create an appropriate mask if the value can have a variable number of digits:

#include <stdio.h>

int get_mask ( int value )
{
  int mask = 1;

  do {
    mask *= 10;
    value /= 10;
  } while ( value > 9 );

  return mask;
}

int main ( void )
{
  int value = 123;

  value %= get_mask ( value );
  printf ( "%d\n", value );

  return 0;
}
Member Avatar for invisal

Alternative way from Narue:

// input your num here.
for (temp = num; temp > 9; temp /= 10)
  printf("%c", '0' + (temp % 10));
Member Avatar for Narue

>Alternative way from Narue:
Maybe I missed something, but I don't think the original question included reversing the digits as well as trimming the most significant digit.

Member Avatar for invisal

>Alternative way from Narue:
Maybe I missed something, but I don't think the original question included reversing the digits as well as trimming the most significant digit.

Sorry. Without much thinking, I jumped to answer this question.

Be a part of the DaniWeb community

We're a friendly, industry-focused community of developers, IT pros, digital marketers, and technology enthusiasts meeting, networking, learning, and sharing knowledge.