C++定义了一个函数，该函数可用于识别容器中的所有数字是否也存在于其他容器中。通过使用在“ algorithm ”标头中定义的“ includes() ”可以实现此任务。下面解释实现。
语法1：使用运算符“ <”
Template :
template
bool includes (initer1 beg1, initer1 end1,
initer2 beg2, initer2 end2,)
Parameters :
beg1 : Input iterator to initial position of first sorted sequence.
end1 : Input iterator to final position of first sorted sequence.
beg2 : Input iterator to initial position of second sorted sequence.
end2 : Input iterator to final position of second sorted sequence.
Return value :
True if every element of 2nd container lies in 1st container.
// C++ code to demonstrate the working of
// includes() implementation 1
#include
using namespace std;
int main()
{
// initializing 1st container
vector arr1 = { 1, 4, 6, 3, 2 };
// initializing 2nd container
vector arr2 = { 1, 2, 4 };
// sorting initial containers
sort(arr1.begin(), arr1.end());
sort(arr2.begin(), arr2.end());
// using include() check if all elements
// of arr2 lie in arr1
if(includes(arr1.begin(), arr1.end(), arr2.begin(), arr2.end()))
cout << "All elements of 2nd container are in 1st container";
else
cout << "All elements of 2nd container are not in 1st container";
}
输出 ：
All elements of 2nd container are in 1st container
语法2：使用比较器
Template :
template
bool includes (initer1 beg1, initer1 end1,
initer2 beg2, initer2 end2, Compare comp)
Parameters :
beg1 : Input iterator to initial position of first sorted sequence.
end1 : Input iterator to final position of first sorted sequence.
beg2 : Input iterator to initial position of second sorted sequence.
end2 : Input iterator to final position of second sorted sequence.
comp : The comparator function that returns a boolean
true/false of the each elements compared. This function
accepts two arguments. This can be function pointer or
function object and cannot change values.
Return value :
True if every element of 2nd container lies in 1st container.
// C++ code to demonstrate the working of
// includes() implementation 2
#include
using namespace std;
// comparator function
bool comp (int i, int j) { return i arr1 = { 1, 4, 6, 3, 2 };
// initializing 2nd container
vector arr2 = { 1, 2, 4 };
// sorting initial containers
sort(arr1.begin(), arr1.end());
sort(arr2.begin(), arr2.end());
// using include() check if all elements
// of arr2 lie in arr1
// using comparator function
if(includes(arr1.begin(), arr1.end(), arr2.begin(), arr2.end(), comp))
cout << "All elements of 2nd container are in 1st container";
else
cout << "All elements of 2nd container are not in 1st container";
}
输出：
All elements of 2nd container are in 1st container
可能的应用：该函数可以潜在地用于查找一套是另一套的子集，还是可以用来确定彩票中奖者的系统，在该系统中，拥有所有彩票号码的人都可以中奖。下文将通过代码进行解释。
// C++ code to demonstrate the application of
// includes()
#include
using namespace std;
int main()
{
// lottery numbers
vector lottery = { 1, 4, 6, 3, 2, 54 , 32 };
// Numbers in user's card
vector user = { 1, 2, 4, 6 };
// sorting initial containers
sort(lottery.begin(), lottery.end());
sort(user.begin(), user.end());
// using include() check if all elements
// of user are present as lottery numbers
if(includes(lottery.begin(), lottery.end(), user.begin(), user.end()))
cout << "User has won lottery ( all numbers are lottey numbers )";
else
cout << "User has not won the lottery";
}
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