二分查找算法
第一种方法：
递归版本：
Error_Code binary_search(const Ordered_list &the_list, const Key &target, int bottom, int top, int &position)
{
Key data;
if (bottom < top){
int mid = bottom + (top - bottom)/2; //注意点
the_list.retrieve(mid, data);
if (data < target)
return binary_search(the_list, target, mid+1, top, position);
else
return binary_search(the_list, target, bottom, mid, position);
} else if (bottom > top){
return not_present;
} else {
position = bottom;
the_list.retrieve(bottom, data);
if (data == target) return success;
else return not_present;
}
}
非递归版本：
Error_Code binary_search(const Ordered_list &the_list, const Key &target, int &position)
{
Key data;
int bottom = 0;
int top = the_lsit.size() - 1;
while (bottom < top){
int mid = bottom + (top - bottom)/2; //注意点
the_list.retrieve(mid, data);
if (data < target)
bottom = mid + 1;
else
top = mid;
}
if (bottom > top){
return not_present;
} else {
position = bottom;
the_list.retrieve(bottom, data);
if (data == target) return success;
else return not_present;
}
}
第二种方法：
递归版本：
Error_Code binary_search(const Ordered_list &the_list, const Key &target, int bottom, int top, int &position)
{
Key data;
if (bottom <= top){
int mid = bottom + (top - bottom)/2; //注意点
the_list.retrieve(mid, data);
if (data == target){
position = mid;
return success;
}else if (data < target)
return binary_search(the_list, target, mid+1, top, position);
else
return binary_search(the_list, target, bottom, mid-1, position);
} else {
return not_present;
}
}
非递归版本：
Error_Code binary_search(const Ordered_list &the_list, const Key &target, int &position)
{
Key data;
int bottom = 0;
int top = the_lsit.size() - 1;
while (bottom <= top){
position = bottom + (top - bottom)/2; //注意点
the_list.retrieve(mid, data);
if (data == target){
return success;
} else if (data < target) {
bottom = position+ 1;
} else {
top = position- 1;
}
}
return not_present;
}