How to get sequence of numbers and then print the last 5? - c

Question

Im trying to make a program that will get sequence from the user that end with 0, and then i want to print the last 5 numbers (not including the 0).
I can assume that the user will input all the numbers in one line and will end it with 0.
I wrote that code but something is wrong with it, I think its something about the scanf line.
Input:
1 6 9 5 2 1 4 3 0
Output: no output
#include <stdio.h>
#define N 5
int main()
{
int arr[N] = {0};
int last_input, j;
printf("please enter more than %d number and than enter 0: \n", N);
last_input = 0;
while (last_input<N) {
scanf(" %d", &j);
if (j == '0') {
last_input = N;
break;
}
else {
arr[last_input] = j;
}
if (last_input==(N-1)) {
last_input=-1;
}
++last_input;
}
printf("The last %d numbers u entered are:\n", N);
for (j=(last_input+1); j<N; ++j) {
printf(" %d", arr[j]);
}
for (j=0; j<last_input; ++j) {
printf(" %d", arr[j]);
}
return 0;
}

Answer 1

This comparison
if (j == '0') {
does not make a sense because the user will try to enter the integer value 0 instead of the value (for example ASCII 30h or EBCDIC F0h) for the character '0'.
You need to write at least
if (j == 0) {
Due to these sub-statements of the if statement
last_input = N;
break;
this for loop
for (j=(last_input+1); j<N; ++j) {
printf(" %d", arr[j]);
}
is never executed and does not make a sense.
This statement
last_input=-1;
results in breaking the order of the N last elements in its output. And moreover the result value of the variable last_input will be incorrect.
You need to move elements of the array one position left. For this purpose you can use a loop of standard C function memmove.
The program can look the following way.
#include <stdio.h>
#include <string.h>
int main( void )
{
enum { N = 5 };
int arr[N];
printf( "Please enter at least not less than %d numbers (0 - stop): ", N );
size_t count = 0;
for (int num; scanf( "%d", &num ) == 1 && num != 0; )
{
if (count != N)
{
arr[count++] = num;
}
else
{
memmove( arr, arr + 1, ( N - 1 ) * sizeof( int ) );
arr[N - 1] = num;
}
}
if (count != 0)
{
printf( "The last %zu numbers u entered are: ", count );
for (size_t i = 0; i < count; i++)
{
printf( "%d ", arr[i] );
}
putchar( '\n' );
}
else
{
puts( "There are no entered numbers." );
}
}
The program output might look like
Please enter at least not less than 5 numbers (0 - stop): 1 2 3 4 5 6 7 8 9 0
The last 5 numbers u entered are: 5 6 7 8 9

Answer 2

I made some changes based on ur comments and now its work fine!
#include <stdio.h>
#define N 5
int main()
{
int arr[N] = {0};
int last_input, j;
printf("please enter more than %d number and than enter 0: \n", N);
last_input = 0;
while (last_input<N) {
scanf("%d", &j);
if (j == 0) {
break;
}
else {
arr[last_input] = j;
}
if (last_input==(N-1)) {
last_input=-1;
}
++last_input;
}
printf("The last %d numbers u entered are:\n", N);
for (j=(last_input); j<N; ++j) {
printf("%d ", arr[j]);
}
for (j=0; j<last_input; ++j) {
printf("%d ", arr[j]);
}
return 0;
}
thank u guys <3.