HDU 5014 Number Sequence （ 构造 ）

#include <cstdio>
#include <cstring>
#include <algorithm>
using namespace std;
#define MAXN 100005
#define CLR( a,b ) memset( a, b, sizeof(a) )
int a[MAXN], vis[MAXN], b[MAXN];

int cnt( int x )
{
    int ct = 0;
    while( x )
    {
        ct++;
        x >>= 1;
    }
    return ct;
}

void Orz()
{
    int n, pos;
    long long ans;
    while( ~scanf( "%d", &n ) )
    {
        CLR( a, 0 ); CLR( b, 0 ); CLR( vis, 0 );
        ans = 0;
        for( int i = n;i >=0; --i )
        {
            if( vis[i] )    continue;
            int ct = cnt( i );
            int tmp =  i ^ ( ( 1 << ct) - 1 );
            b[ tmp ] = i;
            b[ i ] = tmp;
            vis[i] = vis[tmp] = 1;
            ans += ( ( 1 << ct ) - 1 ) << 1;
        }
        printf( "%I64d\n", ans );
        for( int i = 0; i < n; ++i )
        {
            scanf( "%d", &pos );
            printf( "%d ",b[pos] );
        }
        scanf( "%d", &pos );
        printf( "%d\n", b[pos]);
    }
}

int main()
{
    Orz();
    return 0;

}