Наибольшая целая степень двойки, не превосходящая заданного числа n

...
int n, t=1;
cin >> n;
for (;t<n;) t*=2;
cout << t/2;
...

int t;
cin >> t;
int ts=t;
int n=0;
 
while (ts!=0) { ts=ts>>1; ++n;}

unsigned int maxpot(unsigned int n)
{
    unsigned int rv = 0;
    for(; n; n <<= 1)
        rv |= n;
    return (rv >> 1) + 1;
}

unsigned int maxpot(unsigned int n)
{
    unsigned int rv = 0;
    for(; n; n >>= 1) // здесь сдвиг вправо, а не влево
        rv |= n;
    return (rv >> 1) + 1;
}

unsigned int maxpot(unsigned int n)
{
unsigned int rv = 0;
while (n) rv |= n >>= 1;
return ++rv;
}

int n, t=1;
cin >> n;
while (t<n) t <<= 2;
cout << (t >>= 2);

int n;
unsigned int rv = 0;
cin >> n;
while (n) rv |= n >>= 1;
cout << ++rv;

#include <iostream>
#include <time.h>
 
using namespace std;
 
int main()
{
clock_t time;
time = clock();
int n;
 
int t=1;
 
for (int i=2; i<1000000; i++)
{
n=i;
t=1;
while (t<n) t<<=1;
cout << (t>>=1) << endl;
}
 
time = clock() - time;
cout << ((double)time/CLOCKS_PER_SEC); 
system("pause");
return 0;
}

#include <iostream>
#include <time.h>
 
using namespace std;
 
int main()
{
clock_t time;
time = clock();
int n;
 
unsigned int rv;
 
for (int i=2; i<1000000; i++)
{
n=i;
rv=0;
while (n) rv |= n >>= 1;
cout << ++rv << endl;
}
 
time = clock() - time;
cout << ((double)time/CLOCKS_PER_SEC); 
system("pause");
return 0;
}

#include <iostream>
 
 
int main() {
   int power = 1;
   int n = 45;
   
   if ( n >= power << 16 )
      power <<= 16;
   
   if ( n >= power << 8 )
      power <<= 8;
   
   if ( n >= power << 4 )
      power <<= 4;
   
   if ( n >= power << 2 )
      power <<= 2;
   
   if ( n >= power << 1 )
      power <<= 1;
   
   std::cout << power << std::endl;
   
   return 0;
}

int foo(int n){
    int mask=0x80000000;
    int i=31;
    while (!(mask&n)){mask>>=1; --i;}
    return i;
}

int foo(int n){
    int mask=0x80000000;
    int i=31;
    while (!(mask&n)){mask>>=1; --i;}
    return i;
}