C/C++中提高查找速度的小技巧

//在一个int数组中查找某个元素
int find(int A[],int n,int element)
{
 for( int i = 0; i < n; i++ )
 {
  if( A[i] == element )
   return i;
 }
 return -1;
}

//在一个字符串中查找某个字符
int find(string& str,char c)
{ 
 for( int i = 0; i < str.length(); i++ )
 {
  if( str[i] == c )
   return i;
 }
 return -1;
}

//在一个int数组中查找某个元素
int find1(int A[],int n,int element)
{
 if( n <= 0 )
  return -1;
 if( A[--n] == element )
  return n;

 int hold = A[n];
 A[n] = element;
 int i = 0;
 for( ; ; i++ ) 
 {
  if( A[i] == element )
   break;
 }
 A[n] = hold;
 return i < n ? i : -1; 
}

//在一个字符串中查找某个字符
int find1(string& str,char c)
{ 
 int n = str.length();
 if( n <= 0 )
  return -1;
 if( str[--n] == c )
  return n;
 int hold = str[n];
 str[n] = c;
 int i = 0;
 for( ; ; i++ ) 
 {
  if( str[i] == c )
   break;
 }
 str[n] = hold;
 return i < n ? i : -1; 
}

void testFind()
{
 int N = 200000;
 int* A = new int[N];
 A[N-2] = 1; 

 DWORD start = ::GetTickCount64();
 for( int i = 0; i < 10000; i++ ) 
  find(A,N,1);
 DWORD end = ::GetTickCount64();
 cout <<"优化前：" << end - start <<" 毫秒" << endl; 

 start = ::GetTickCount64(); 
 for( int i = 0; i < 10000; i++ ) 
  find1(A,N,1);
 end = ::GetTickCount64();
 cout <<"优化后：" << end - start <<" 毫秒" << endl; 
}