#include <stdio.h>
#include <stdint.h>
/* Print a 64-bit number as bits (no leading zeros trimmed) */
void print_bits(uint64_t v, int width) {
for (int i = width - 1; i >= 0; i--) {
putchar((v & (1ULL << i)) ? '1' : '0');
}
}
/*
exact_bit_set:
----------------
Returns 1 only if:
• pos1 and pos2 are valid (>= 0, < 64, and not equal)
• value has EXACTLY those two bits set
• all other bits are OFF
Bit positions are ZERO‑BASED from the RIGHT (LSB = position 0).
*/
int exact_bit_set(int pos1, int pos2, uint64_t value) {
if (pos1 < 0 || pos2 < 0 || pos1 >= 64 || pos2 >= 64)
return 0;
if (pos1 == pos2)
return 0;
uint64_t mask = (1ULL << pos1) | (1ULL << pos2);
return value == mask;
}
int main(void) {
struct Test {
uint64_t value;
int x, y;
int width;
};
struct Test tests[] = {
{0b1000010000ULL, 4, 9, 10},
{0b0010000010ULL, 1, 7, 10},
{0b0000100100ULL, 2, 5, 10},
{0b1000010000ULL, 3, 9, 10},
{0b1001010000ULL, 4, 9, 10},
{0b1111111111ULL, 4, 9, 10},
{0b0000000000ULL, 4, 9, 10},
{0b1000010000ULL, 4, 8, 10},
{1ULL, 0, 0, 1},
{1ULL, 0, 1, 1},
{0ULL, 1, 1, 1}
};
int count = sizeof(tests) / sizeof(tests[0]);
for (int i = 0; i < count; i++) {
uint64_t v = tests[i].value;
int x = tests[i].x;
int y = tests[i].y;
print_bits(v, tests[i].width);
printf(" bits(%d, %d) -> %s\n",
x, y,
exact_bit_set(x, y, v) ? "true" : "false");
}
return 0;
}
/*
OUTPUT:
1000010000 bits(4, 9) -> true
0010000010 bits(1, 7) -> true
0000100100 bits(2, 5) -> true
1000010000 bits(3, 9) -> false
1001010000 bits(4, 9) -> false
1111111111 bits(4, 9) -> false
0000000000 bits(4, 9) -> false
1000010000 bits(4, 8) -> false
1 bits(0, 0) -> false
1 bits(0, 1) -> false
0 bits(1, 1) -> false
*/
