指定長度的strstr函式

前一段工作中用到了，找了幾個方法。都實現了一下，測試了下，都差不多，glibc的實現方法相比還是快一些，stristrex也不慢，至於qi_strnstr，是自己的乙個想法實現的，不過可悲的是，他是最慢的。

char *glibc_strnstr (const char *phaystack, const char *pneedle, int len)

while (a != b);
}		if (!(c = *++needle))
goto foundneedle;
++needle;
goto jin;
for (;;)
else
a = *++haystack;
do}while ((a = *++haystack) != c);
}crest:
while (*++rhaystack == (a = *++needle) && pend > rhaystack);
needle = rneedle;	/* took the register-poor aproach */
}if(!a)
break;
}}	}
foundneedle:
return (char *) haystack;
ret0:
return 0;
}char *qi_strnstr (const char *phaystack, const char *pneedle, int len)
else if( ilen >= 4 )
else if( ilen >= 2 )
else if( ilen >= 1 )
}if(ilen == 0)
return (char*)pcur;	}	
return null;
}static char* _stristrex( const char * src, long src_len, const char * substr, long substr_len )
ch = *substr;		
chothercase = ch;	
if ( ch >= 'a' && ch <= 'z')		
else if (ch > 'a' && ch <= 'z')					
p = src;	
pend = p + src_len;
while ( p < pend )		
}	p++;	}	
return null;	} 
static char* strnstr( const char * src, long src_len, const char * substr, long substr_len )
p = src;	
pend = p + src_len - substr_len;
while ( p < pend )		
}p++;	}	
return null;	
}

static void test_strnstr()

printf("glibc_strnstr耗時 = %d\n\n", gettickcount()-start);
cs = 100*1000000;
start = gettickcount();
printf("start = %llu,cs=%d\n", start,cs);
while(cs--)
printf("qi_strnstr耗時 = %d\n\n", gettickcount()-start);
cs = 100*1000000;
start = gettickcount();
printf("start = %llu,cs=%d\n", start,cs);
while(cs--)
printf("_stristrex耗時 = %d\n\n", gettickcount()-start);
cs = 100*1000000;
start = gettickcount();
printf("start = %llu,cs=%d\n", start,cs);
while(cs--)
printf("strnstr耗時 = %d\n\n", gettickcount()-start);
				
指定長度路徑數
time limit 1000 ms memory limit 65536 kib submit statistic problem description 題目給出乙個有n個節點的有向圖，求該有向圖中長度為k的路徑條數。方便起見，節點編號為1,2,n，用鄰接矩陣表示該有向圖。該有向圖的節點數不少於...
				
指定長度路徑數
time limit 1000 ms memory limit 65536 kib submit statistic problem description 題目給出乙個有n個節點的有向圖，求該有向圖中長度為k的路徑條數。方便起見，節點編號為1,2,n，用鄰接矩陣表示該有向圖。該有向圖的節點數不少於...
				
指定長度路徑數
problem description 題目給出乙個有n個節點的有向圖，求該有向圖中長度為k的路徑條數。方便起見，節點編號為1,2,n，用鄰接矩陣表示該有向圖。該有向圖的節點數不少於2並且不超過500.例如包含兩個節點的有向圖，圖中有兩條邊1 2 2 1 長度為1的路徑有兩條 1 2 和 2 1 長...