solve.c

#include <stdio.h>
#include <stdlib.h>
#define MAX(a, b) ((a) > (b) ? (a) : (b));
#include <assert.h>
#include <limits.h>
int rangeBitwiseAnd(int m, int n) {
	if (m == n)
		return m;
	if (m == 0)
		return 0;
	int base = 1;
	int t = n;
	while ((t >> 1)) {
		base <<= 1;
		t >>= 1;
	}
	int ans = 0;
	while (base) {
		int a = base & m;
		int b = base & n;
		if (a != b)
			return ans;
		ans |= a;
		base >>= 1;
	}
	return ans;
}
int slowRangeBitwiseAnd(int m, int n) {
	int ans = n;
	for (int i = n - 1; i >= m && ans; --i)
		ans &= i;
	return ans;
}
int midRangeBitwiseAnd(int m, int n)
{
	int base = 1;
	int t = n;
	while ((t >> 1)) {
		base <<= 1;
		t >>= 1;
	}
	if (m < base)
		return 0;
	int ans = n;
	for (int i = n - 1; i >= m; --i)
		ans &= i;
	return ans;
}
int fastRangeBitwiseAnd(int m, int n)
{
	return rangeBitwiseAnd(m, n);
}
int slow(int m, int n)
{
	return slowRangeBitwiseAnd(m, n);
}
int mid(int m, int n) {
	return midRangeBitwiseAnd(m, n);
}

int fast(int m, int n)
{
	return fastRangeBitwiseAnd(m, n);
}
int test(int i, int j)
{
	int s = slow(i, j);
	int m = mid(i, j);
	int f = fast(i, j);
	if (s != f) {
		printf("[%d, %d], slow = %d, fast = %d\n", i, j, s, f);
		return 1;
	}
	if (s != m) {
		printf("[%d, %d], slow = %d, mid = %d\n", i, j, s, m);
		return 1;
	}
	return 0;
}
int main(int argc, char **argv)
{
	for (int i = 0; i < 200; i ++)
		for (int j = i; j < 200; j++)
			if (test(i, j)) {
				return 1;
			}

	return 0;
}