C++ is_partitioned()
C++算法is_partitioned()
C++算法 is_partitioned()用于测试范围[first，last)是否根据谓词。换句话说，范围中所有满足谓词的元素都在序列的开头。
如果范围为空，则返回true。
语法
template <class InputIterator, class UnaryPredicate>
bool is_partitioned (InputIterator first, InputIterator last, UnaryPredicate pred);
参数
first: 指向范围中第一个元素的输入迭代器。
last: 指向该范围中最后一个元素的输入迭代器。
pred : 用户定义的一元谓词函数，该函数对期望找到的元素返回true
返回值
如果范围为空或被给定谓词pred分区，则此函数返回true，否则返回false。
复杂度
复杂度在[first，last)范围内是线性的: 为每个元素调用pred直到发现不匹配。
数据竞争
访问[first，last)范围内的对象。
每个元素都被访问一次。
异常
如果pred或迭代器上的操作抛出异常，则此函数将引发异常。
请注意，无效参数ca使用未定义的行为。
示例1
让我们看一个简单的示例来演示is_partitioned()的使用:
#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;
int main()
{
vector<int> v = {1, 2, 3, 4, 5};
cout<<"Before Partition: ";
for_each(v.begin(), v.end(), [](int v) {
cout << v << " ";
});
auto pred = [](int x) { return x % 2 == 0; };
// Divide it into an even group and an odd group
partition(v.begin(), v.end(), pred);
cout<<"\nAfter partition : ";
for_each(v.begin(), v.end(), [](int x) {
cout << x << " ";
});
cout<<"\n\nIs it partitioned?"<<endl;
// Is it divided into an even group and an odd group?
if (is_partitioned(v.begin(), v.end(), pred)) {
cout << "Yes,It is Partitioned" << endl;
}
else {
cout << "No,It is not Partitioned" << endl;
}
return 0;
}
输出:
Before Partition: 1 2 3 4 5
After partition : 4 2 3 1 5
Is it partitioned?
Yes,It is Partitioned
示例2
让我们看另一个简单的示例:
#include <iostream>
#include <algorithm>
#include <vector>
// Defining the BinaryFunction
bool pred(int a)
{
return (a % 2 == 0);
}
using namespace std;
int main()
{
// Declaring first vector
vector<int> v1 = { 2, 4, 6, 3, 5, 7, 9 };
// Using std::is_partitioned
bool b = std::is_partitioned(v1.begin(), v1.end(), pred);
if (b == 1) {
cout << "All the even no. are present before odd no.";
} else {
cout << "All the even no. are not present before odd no.";
}
// Inserting an even no. at the end of v1
// so std::is_partitioned returns false
v1.push_back(16);
// Now again using std::is_partitioned
b = std::is_partitioned(v1.begin(), v1.end(), pred);
if (b == 1) {
cout << "\nAll the even no. are present before odd no.";
} else {
cout << "\nAll the even no. are not present before odd no.";
}
return 0;
}
输出:
All the even no. are present before odd no.
All the even no. are not present before odd no.
示例3
让我们看另一个简单的示例:
#include <algorithm>
#include <array>
#include <iostream>
int main()
{
std::array<int, 9> v = { 1, 2, 3, 4, 5, 6, 7, 8, 9 };
auto is_even = [](int i){ return i % 2 == 0; };
std::cout.setf(std::ios_base::boolalpha);
std::cout << std::is_partitioned(v.begin(), v.end(), is_even) << ' ';
std::partition(v.begin(), v.end(), is_even);
std::cout << std::is_partitioned(v.begin(), v.end(), is_even) << ' ';
std::reverse(v.begin(), v.end());
std::cout << std::is_partitioned(v.begin(), v.end(), is_even);
}
输出:
示例4
让我们看另一个简单的示例:
#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;
int main()
{
vector<int> v = {11, 2, 3, 4, 15, 12};
cout<<"Before Partition: ";
for_each(v.begin(), v.end(), [](int v) {
cout << v << " ";
});
auto pred = [](int x) { return x < 10; };
// Divide it into an even group and an odd group
partition(v.begin(), v.end(), pred);
cout<<"\nAfter partition: ";
for_each(v.begin(), v.end(), [](int x) {
cout << x << " ";
});
cout<<"\n\nIs it partitioned?"<<endl;
// Is it divided into an even group and an odd group?
if (is_partitioned(v.begin(), v.end(), pred)) {
cout << "Yes, It is Partitioned." << endl;
}
else {
cout << "No, It is not Partitioned." << endl;
}
return 0;
}
输出:
Before Partition: 11 2 3 4 15 12
After partition: 4 2 3 11 15 12
Is it partitioned?
Yes, It is Partitioned.
