二分查找
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二分查找法是算法课必讲的查找算法之一,它的理论学计算机的都知道。离开学校多年,很多东西都忘光了,如今重新复习算法,顺便整理整理,也作为学习的笔记。
//在数组data中查找值为key的元素,找到返回下标(zero based),否则返回-1
template<typename T>
int binsrch(T *data, unsigned len, T key );
template<typename T>
int binsrch(T *data, unsigned len, T key )
...{
if( len < 1 )
...{
return -1;
}
unsigned low = 0;
unsigned high = len - 1;
unsigned mid = 0;
while( low <= high )
...{
//计算mid = (high + low) / 2,用(high+low)/2当high+low溢出时会出错
mid = low + ( ( high - low ) >> 1 );
if( key == data[mid] )
...{
return mid;
}
else if( key > data[mid] )
...{
low = mid+1;
}
else
...{
high = mid - 1;
}
}
return -1;
}
int _tmain(int argc, _TCHAR* argv[])
...{
int arr[] = ...{1,3};
int pos = binsrch( arr, sizeof(arr)/sizeof(arr[0]), 3 );
return 0;
}
template<typename T>
int binsrch(T *data, unsigned len, T key );
template<typename T>
int binsrch(T *data, unsigned len, T key )
...{
if( len < 1 )
...{
return -1;
}
unsigned low = 0;
unsigned high = len - 1;
unsigned mid = 0;
while( low <= high )
...{
//计算mid = (high + low) / 2,用(high+low)/2当high+low溢出时会出错
mid = low + ( ( high - low ) >> 1 );
if( key == data[mid] )
...{
return mid;
}
else if( key > data[mid] )
...{
low = mid+1;
}
else
...{
high = mid - 1;
}
}
return -1;
}
int _tmain(int argc, _TCHAR* argv[])
...{
int arr[] = ...{1,3};
int pos = binsrch( arr, sizeof(arr)/sizeof(arr[0]), 3 );
return 0;
}