CareerCup

i is the number of input

int count=0;

if(i&0xffff0000){ count |= 1<<4; i = (i&0xffff0000)>>4;}
...

#include <iostream>
#include <string>
#include <vector>
#include <list>
#include <assert.h>
#include <algorithm>

using namespace std;

int main(int argc, char* argv[])
{
int i = 0;
cin>>i;
int index = 0, temp = i;

if(temp&0xffff0000)
{
index += 16;
temp = (temp&0xffff0000)>>16;
}

if(temp&0x0000ff00)
{
index += 8;
temp = (temp&0x0000ff00)>>8;
}

if(temp&0x000000f0)
{
index += 4;
temp = (temp&0x000000f0)>>4;
}

if(temp&0x0000000c0)
{
index += 2;
temp = (temp&0x0000000c0)>>2;
}

if(temp&0x00000002)
++index;

cout<<index<<endl;
return 0;
}

//geniusxsy's post actually said all, I just want to check if I can finish it in 15mins

int most_significatn_bit(const unsigned int input)
{
if (input == 0) {
return 0;
}

unsigned int n = 0x80000000;
int nIndx = 32;
for(int i = 32; i > 0; i --) {
if (input & n) {
return i;
}
n = n >> 1;
}
return 0;
}

int most_sign_One(int input)
	{

		int tmp = 1;
		int i = 0;
		
		while(input >= tmp)
		{
			i++;
			tmp = tmp<<1;
		}

	return i-1;

	}

Depending upon the architecture of the machine, the most significant bit is either the left most or the right most. So one way could be to left shift or right shift by 1

i think counting the no of leading zeros i.e from M.S.B of any no could be a solution.

// find the position of the most significant 1 bit?
int GetFirstMsb1(int num)
{
if (!num)
return -1;

int pos = 0, i = 0;
unsigned int mask = 0xff000000;
int n = num & mask;
do
{
if (n)
{
if (n >= 128)
pos = 0 + i;
else if (n >= 64)
pos = 1 + i;
else if (n >= 32)
pos = 2 + i;
else if (n >= 16)
pos = 3 + i;
else if (n >= 8)
pos = 4 + i;
else if (n >= 4)
pos = 5 + i;
else if (n >= 2)
pos = 6 + i;
else if (n >= 1)
pos = 7 + i;

return pos;
}

mask >>= 8;
n = num & mask;
i += 8;
}
while (i < sizeof(int) * 8);

return pos;
}

The best way to do,for an integer, is to find out the log base 2,as suggested by sumo.

int bit = !(n ^ (1 << sizeof(int)))

log(n)/log(2)