#include <stdio.h>
#include <stdlib.h>
/*
removeBitsAndShift(number, positions, count)
--------------------------------------------
Removes multiple bit positions from a number and shifts the remaining bits
right to fill the gaps.
Important:
Bits must be removed from highest → lowest position.
Otherwise earlier removals shift the positions of later ones.
*/
int removeBitsAndShift(int number, const int *positions, int count) {
// Copy and sort positions descending
int *sorted = malloc(count * sizeof(int));
for (int i = 0; i < count; i++) sorted[i] = positions[i];
// Simple bubble sort descending
for (int i = 0; i < count - 1; i++) {
for (int j = 0; j < count - i - 1; j++) {
if (sorted[j] < sorted[j + 1]) {
int tmp = sorted[j];
sorted[j] = sorted[j + 1];
sorted[j + 1] = tmp;
}
}
}
int result = number;
for (int i = 0; i < count; i++) {
int pos = sorted[i];
int left = result >> (pos + 1); // bits above removed bit
int right = result & ((1 << pos) - 1); // bits below removed bit
result = (left << pos) | right; // merge
}
free(sorted);
return result;
}
/*
printBinary(n)
--------------
Prints a 32-bit binary representation of an integer.
*/
void printBinary(int n) {
for (int i = 31; i >= 0; i--) {
printf("%d", (n >> i) & 1);
if (i % 4 == 0) printf(" ");
}
}
int main() {
int number = 1234; // 0000 0000 0000 0000 0000 0100 1101 0010
int positions[] = {1, 3, 7}; // remove bits 1, 3, 7 (0 = LSB)
int count = sizeof(positions) / sizeof(positions[0]);
printf("Original number in binary:\n");
printBinary(number);
int result = removeBitsAndShift(number, positions, count);
printf("\n\nNumber after removing bits {1, 3, 7} and shifting remaining bits:\n");
printBinary(result);
printf("\n\nResult as integer: %d\n", result);
return 0;
}
/*
run:
Original number in binary:
0000 0000 0000 0000 0000 0100 1101 0010
Number after removing bits {1, 3, 7} and shifting remaining bits:
0000 0000 0000 0000 0000 0000 1001 0100
Result as integer: 148
*/
