90%程序员在充足时间都无法写对的2分查找算法实现【C++版本】

#include <cstdlib>

#include <iostream>

using namespace std;

typedef unsigned int u_int ;

template<typename T> class CBSearch

{

public:

static int find(const T& target, const T* array, u_int size)

{

u_int pos1=0, pos2=size-1;

while(pos2 >= pos1){

u_int i = (pos2 + pos1)/2;

if(i == pos1){

if(target == *(array+pos1))

return _shift(target, array, pos1);

else if(target == *(array+pos2))

return pos2;

else

return -1;

}

else{

if(target > *(array + i))

pos1 = i;

else if(*(array + i) > target)

pos2 = i;

else

return _shift(target, array, i);

}

}

return -1;

}

protected:

static inline u_int _shift(const T& target, const T* array, u_int pos)

{

while(pos > 0){

if(array[pos-1] == target) --pos;

else break;

}

return pos;

}

};

template<typename T>class CBSearchRecursion

{

public:

/*

好的实现基于清晰的构思，方便的调试，有效的验证

构思：（ 写适用于各种情况的代码是神人.....可惜我不是......)

每次调用过程中逐渐缩小查找范围，当范围足够小就用最直观的实现方式

*/

static int find(const T& target, const T*array, u_int size)

{

if(size <= 0)

return -1;

int mid = (size - 1)/2;

if(array[mid] == target)

return _shift(target, array, mid);

else if(array[mid] > target)

return find(target, array, mid);

else{

if(mid == 0){ // size == 2 || size == 1

if(size == 1)

return array[mid] == target?mid:-1;

else{

if(array[mid] == target)

return mid;

else if(array[++mid] == target)

return mid;

else

return -1;

}

}

else{

int tmp = find(target, array+mid, size-mid);

tmp = tmp==-1?-1:mid + tmp ;

return _shift(target, array, tmp);

}

}

}

protected:

static u_int _shift(const T& target, const T* array, u_int pos)

{

while(pos > 0){

if(array[pos-1] == target) --pos;

else break;

}

return pos;

}

};

int main(int argc, char *argv[])

{

while(1){

u_int arr_size = 0;

cout << "input arr size:";

cin >> arr_size;

int* arr = new int[arr_size];

for(u_int i = 0; i < arr_size; ++i){

cin >> *(arr+i);

}

while(1){

int k = 0;

cout << "to find your num:(0 to break)";

cin >> k;

if(k ==0 ) break;

//int pos = CBSearch<int>::find(k, arr, arr_size);

int pos = CBSearchRecursion<int>::find(k, arr, arr_size);

cout << "pos=" << pos << endl;

}

}

system("PAUSE");

return EXIT_SUCCESS;

}