這是一個全排列算法的C++模板, 與STL中泛型算法next_permutation的功能是一樣的。
template < typename T >
bool _next_permutation( T *first, T *last );
#define N 8
int main(int argc, char* argv[])
{
int i;
int y = 1;//序號
char a[N];
for ( i=0; i<N; i++ )
{
a[i] = i + 1 + 64 + 32;
}
long t0 = time( NULL );
do
{
cout << y << " ---> ";
for ( i = 0; i<N; i++ ) cout << a[i];
cout << endl;
y++;
}while( _next_permutation( &a[0], &a[N] ) );
long t1 = time( NULL ) - t0;
cout << t1 << endl;//當N為8時耗時130秒，與泛型算法next_permutation用時一樣
return 0;
}
template < typename T >
bool _next_permutation( T *first, T *last )
{
int i;
int j;
int x = -1;
int rang = last - first;
for ( i=0; i<rang-1; i++ )
{
if ( *( first+i ) <= *( first+i+1 ) )
{
x = i;
}
}
if ( x != -1 )
{
for ( i=x; i<rang; i++ )
{
if ( *( first+x ) <= *( first+i ) )
{
j = i;
}
}
_swap( *( first+x ), *( first+j ) );
for ( i=x+1; i<rang; i++ )
{
if ( i != rang + x - i )
{
int nSwap = rang + x - i;
_swap( *( first+i ), *( first+ ( rang+x-i ) ) );
}
if ( ( i + 1 ) * 2 > rang + x )
{
break;
}
}
}
if ( -1 == x ) return false;
else return true;
}
template < typename T >
void _swap( T &a, T &b )
{
a = a + b;
b = a - b;
a = a - b;
}
posted on 2010-08-20 10:51
崔佳星 閱讀(2001)
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