Member Avatar for Stefan_2

This is what I have to code.
Input an array of numbers(any numbers that user inputs from standard input, aka keyboard), remove numbers from array that are not 0 and 1. Thay array should now be bitwise moved with << or >> (again user choses the number of spaces moved and a type of move). After all of that turn that array into a binary number. Max number of elements is defined as a header with #define max_num_el 255.

I have issues with part of code that need me to move elements of array and turning an array into binary number.

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Quick diagnosis and a compact plan (responding to , echoing 's request for code and 's temporary-variable hint): three separate issues cause the observed behavior — using the C bit-shift operators on integer elements instead of shifting array positions, unsafe/incorrect input handling, and attempting to pack an arbitrary-length bit array into a fixed-width integer (overflow risk for >64 bits). The correct choices are: represent bits as bytes (uint8_t), move the element positions with memmove/loops, and only use <</>> on integers when you have packed bits into an integer type that can hold them.

Safe element shifts (move positions, fill vacated slots with 0):

#include <string.h>

void shift_left(uint8_t *a, size_t n, size_t p) {
    if (p >= n) { memset(a, 0, n); return; }
    memmove(a, a + p, n - p);
    memset(a + n - p, 0, p);
}

void shift_right(uint8_t *a, size_t n, size_t p) {
    if (p >= n) { memset(a, 0, n); return; }
    memmove(a + p, a, n - p);
    memset(a, 0, p);
}

Converting the bit array to a numeric value:

  • If n <= 64, pack into unsigned long long safely:
    unsigned long long bits_to_ull(const uint8_t *a, size_t n) {
  unsigned long long v = 0;
  for (size_t i = 0; i < n; ++i) v = (v << 1) | (a[i] & 1);
  return v;
}
  • If n > 64, produce a string of '0'/'1' or use a big-integer library (GMP) / a custom bitset; never assume unsigned long can hold 255 bits.

Practical fixes: use int main(void), check scanf return values and use scanf("%d", &x) (no trailing dot), prefer fgets+strtol for robust input, use uint8_t for per-bit storage, and test shifts with small arrays first to confirm behavior. These changes reconcile the observed multiplication-from-<< with the intended array-index shift and avoid overflow when converting to a binary number.

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Member Avatar for Ancient Dragon

Post the code you have written so that we can see where your "issues" are.

Member Avatar for ravi_14

use temporary variable for moving the items and for binary conversion ,you can easily write code ..

Member Avatar for Stefan_2 
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#define max_br_el 255

void main (){
    int p,k,j,n,i,temp,r;
    unsigned long a[max_br_el], b[max_br_el];
    while(1){
        printf("\nEnter number of array elements (between 1 i 255)\n");
        scanf("%d", &n);
        if(n>0 && n<=max_br_el){
            for(i=0 ; i<n ; i++){
                printf("Enter %d. elements of array\n", i);
                scanf("%d.", &a[i]);
            }
            /* Removing nums not 0 and 1 */
            for(i=0 , k=0  ; i<n ; i++){
                if(a[i] == 0 || a[i] == 1){
                    a[k] = a[i];
                    k++;
                }
            }
            n=k;
            for(k=0 ; k<n ; k++){
                printf("%d\t" , a[k]);
            }
            /* My try on moving elements manualy (it has to be done with                  << and >> but I don't know how. Whenever I try to use << and                  >> I get element_of_array*2^n (where and n is number of                      spaces that needs to be moved. */
            printf("\n");
            printf("\nEnter for how many spaces you want to move\n");
            scanf("%d", &p);
            for(r=0 ; r<n; r++){
                b[r] = a[k-p];

            }
            printf("\n");
            for(r=0 ; r<n ; r++){
                printf("%d" , b[r]);
            }
        }
        else{
            exit(1);
        }
    }
}

/* This is code so far. I still don't have part about binary conversion made, because I have bigger issues with << and >>. Here I tryed implementing manual moving of elements of array but it didn't work. Thanks for help. */

Member Avatar for Stefan_2

I'll show the code tonight, and making this question to solved.

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