再來一道簡單點的。。。這道用鄰接表+hash就OK了
http://acm.hdu.edu.cn/showproblem.php?pid=1524
神奇的圖博弈
http://acm.hdu.edu.cn/showproblem.php?pid=1809根據(jù)遞歸求出沒副圖的sg值，然后異或
但是如果暴力遞歸的話會做很多重復(fù)的搜索
所以hash一下用記憶化搜索
要整個地圖的狀態(tài)來hash
我搞了半天搞不定
后來查到神奇的字符hash方法
用了一下果然很靈
不過現(xiàn)在還是不太清楚為什么這樣可以hash
// RS Hash Function
unsigned int RSHash(char* str)
{
unsigned int b = 378551 ;
unsigned int a = 63689 ;
unsigned int hash = 0 ;
while (*str)
{
hash = hash * a + (*str ++ );
a *= b;
}
return (hash & 0x7FFFFFFF );
}
// JS Hash Function
unsigned int JSHash(char* str)
{
unsigned int hash = 1315423911 ;
while (*str)
{
hash ^= ((hash << 5 ) + (*str ++ ) + (hash >> 2 ));
}
return (hash & 0x7FFFFFFF );
}
// P. J. Weinberger Hash Function
unsigned int PJWHash(char* str)
{
unsigned int BitsInUnignedInt = (unsigned int )( sizeof (unsigned int)*8 );
unsigned int ThreeQuarters = (unsigned int )((BitsInUnignedInt*3 ) / 4 );
unsigned int OneEighth = (unsigned int )(BitsInUnignedInt / 8 );
unsigned int HighBits = (unsigned int )( 0xFFFFFFFF ) << (BitsInUnignedInt - OneEighth);
unsigned int hash = 0 ;
unsigned int test = 0 ;
while (*str)
{
hash = (hash << OneEighth) + (*str ++ );
if ((test = hash & HighBits) != 0 ) {
hash = ((hash ^ (test >> ThreeQuarters)) & ( ~ HighBits));
}
}
return (hash & 0x7FFFFFFF );
}
// ELF Hash Function
unsigned int ELFHash(char* str)
{
unsigned int hash = 0 ;
unsigned int x = 0 ; while (*str)
{
hash = (hash << 4 ) + (*str ++ );
if ((x = hash & 0xF0000000L ) != 0 ) {
hash ^= (x >> 24 );
hash &= ~ x;
}
}
return (hash & 0x7FFFFFFF );
}
// BKDR Hash Function
unsigned int BKDRHash(char* str)
{
unsigned int seed = 131 ; // 31 131 1313 13131 131313 etc..
unsigned int hash = 0 ;
while (*str)
{
hash = hash*seed + (*str ++ );
}
return (hash & 0x7FFFFFFF );
}
// SDBM Hash Function
unsigned int SDBMHash(char* str)
{
unsigned int hash = 0 ;
while (*str)
{
hash = (*str ++ ) + (hash << 6 ) + (hash << 16 ) - hash;
}
return (hash & 0x7FFFFFFF );
}
// DJB Hash Function
unsigned int DJBHash(char* str)
{
unsigned int hash = 5381 ;
while (*str)
{
hash += (hash << 5 ) + (*str ++ );
}
return (hash & 0x7FFFFFFF );
}
// AP Hash Function
unsigned int APHash(char* str)
{
unsigned int hash = 0 ;
int i;
for (i = 0 ;*str; i ++ )
{
if ((i & 1 ) == 0 ) {
hash ^= ((hash << 7 ) ^ (*str ++ ) ^ (hash >> 3 ));
} else {
hash ^= ( ~ ((hash << 11 ) ^ (*str ++ ) ^ (hash >> 5 )));
}
}
return (hash & 0x7FFFFFFF );
}
posted on 2009-03-01 06:13
shǎ崽 閱讀(313)
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