极客笔记C++ 算法 reverse()函数
C++算法 reverse() 函数用于反转范围[first, last)内的元素的顺序。
语法
template <class BidirectionalIterator>
void reverse (BidirectionalIterator first, BidirectionalIterator last);
注意：BidirectionalIterator是一种迭代器，可用于在正向和反向方向访问容器的任何元素。
参数
first ：指向正在翻转元素的范围中第一个元素的位置的双向迭代器。
last ：指向正在翻转元素的范围中最后一个元素之后位置的前向迭代器。
返回值
无
复杂度
复杂度与范围[first, last)的长度成线性关系 ：交换元素。
数据竞争
范围[first, last)中的对象被修改。
异常
如果交换元素或迭代器操作抛出异常，则此函数抛出异常。
注意：无效的参数导致未定义行为。
示例1
让我们来看一个简单的示例，翻转给定的字符串：
#include <algorithm>
#include <iostream>
#include <string>
using namespace std;
int main() {
string str = "Hello Myself Nikita";
cout << "Before Reverse : "<< str << endl;
reverse(str.begin(), str.end());
cout <<"After Reverse : " << str << endl;
return 0;
}
输出：
Before Reverse : Hello Myself Nikita
After Reverse : atikiN flesyM olleH
示例2
让我们看另一个简单的示例来逆转数值范围：
#include <vector>
#include <algorithm>
#include <iostream>
using namespace std;
int main( ) {
vector <int> v1;
vector <int>::iterator Iter1;
int i;
for ( i = 0 ; i <= 9 ; i++ )
{
v1.push_back( i );
}
cout << "The original vector v1 is:\n ( " ;
for ( Iter1 = v1.begin( ) ; Iter1 != v1.end( ) ; Iter1++ )
cout << *Iter1 << " ";
cout << ")." << endl;
// Reverse the elements in the vector
reverse (v1.begin( ), v1.end( ) );
cout << "The modified vector v1 with values reversed is:\n ( " ;
for ( Iter1 = v1.begin( ) ; Iter1 != v1.end( ) ; Iter1++ )
cout << *Iter1 << " ";
cout << ")." << endl;
return 0;
}
输出：
The original vector v1 is:
( 0 1 2 3 4 5 6 7 8 9 ).
The modified vector v1 with values reversed is:
( 9 8 7 6 5 4 3 2 1 0 ).
示例3
让我们看另一个简单的示例：
#include<iostream>
#include<algorithm>
#include<vector>
using namespace std;
int main()
{
vector <int> v ;
// Inserting elements in vector
for (int i = 0; i < 8; i++)
v.push_back(i+10);
// Displaying elements of vector
vector <int> :: iterator it;
cout<<"Before: ";
for (it = v.begin(); it != v.end(); it++)
cout << (*it) << " ";
cout << "\n\nReverse only from index 5 to 7 in array:\n";
// Reversing elements from index 5 to index 7
reverse(v.begin() + 5, v.begin() + 8);
for (it = v.begin(); it != v.end(); it++)
cout << (*it) << " ";
// Reversing directly from beginning to end
cout << "\nReverse full array:\n";
int a[] = {4, 5, 6, 7};
reverse(begin(a), end(a));
// Print the array
cout << a[0] << a[1] << a[2] << a[3] << '\n';
return 0;
}
输出结果：
Before: 10 11 12 13 14 15 16 17
Reverse only from index 5 to 7 in array:
10 11 12 13 14 17 16 15
Reverse full array:
7654
示例4
看看另一个简单的示例：
#include <iostream>
#include <algorithm>
#include <vector>
#include <iomanip>
using namespace std;
void print(string a[], int N)
{
for(int i = 0; i < N; i++)
{
cout << (i + 1) << ". " << setw(5)
<< a[i] << " ";
}
cout << endl;
}
int main()
{
string s[] = {"George", "John", "Nik", "Alice", "Bob", "Watson"};
cout << "Original order : ";
print(s, 6);
cout << "\nReversing the order ... " << endl;
reverse(s, s + 6);
cout << "Reversed order : ";
print(s, 6);
}
输出：
Original order : 1. George 2. John 3. Nik 4. Alice 5. Bob 6. Watson
Reversing the order ....
Reversed order : 1. Watson 2. Bob 3. Alice 4. Nik 5. John 6. George