# 算法库：C++魔术师STL算法用法示例

2021年3月12日13:07:53 发表评论 844 次浏览

## 本文概述

STL有大量的算法, 可用于所有<algorithm>库函数：请参见

.

1. 分类(first_iterator, last_iterator)–对给定向量进行排序。
2. 反向(first_iterator, last_iterator)–反转向量。
3. * max_element(first_iterator, last_iterator)–查找向量的最大元素。
4. * min_element(first_iterator, last_iterator)–查找向量的最小元素。
5. 累积(first_iterator, last_iterator, 总和的初始值)–是否对向量元素求和

## CPP

``````// A C++ program to demonstrate working of sort(), // reverse()
#include <algorithm>
#include <iostream>
#include <vector>
#include <numeric> //For accumulate operation
using namespace std;

int main()
{
// Initializing vector with array values
int arr[] = {10, 20, 5, 23 , 42 , 15};
int n = sizeof (arr)/ sizeof (arr[0]);
vector< int > vect(arr, arr+n);

cout << "Vector is: " ;
for ( int i=0; i<n; i++)
cout << vect[i] << " " ;

// Sorting the Vector in Ascending order
sort(vect.begin(), vect.end());

cout << "\nVector after sorting is: " ;
for ( int i=0; i<n; i++)
cout << vect[i] << " " ;

// Reversing the Vector
reverse(vect.begin(), vect.end());

cout << "\nVector after reversing is: " ;
for ( int i=0; i<6; i++)
cout << vect[i] << " " ;

cout << "\nMaximum element of vector is: " ;
cout << *max_element(vect.begin(), vect.end());

cout << "\nMinimum element of vector is: " ;
cout << *min_element(vect.begin(), vect.end());

// Starting the summation from 0
cout << "\nThe summation of vector elements is: " ;
cout << accumulate(vect.begin(), vect.end(), 0);

return 0;
}``````

``````Vector is: 10 20 5 23 42 15
Vector after sorting is: 5 10 15 20 23 42
Vector after reversing is: 42 23 20 15 10 5
Maximum element of vector is: 42
Minimum element of vector is: 5
The summation of vector elements is: 115``````

6.count(first_iterator, last_iterator, x)–计算向量中x的出现。

7.查找(first_iterator, last_iterator, x)

–如果向量中不存在元素, 则指向向量的最后一个地址((name_of_vector).end())。

## CPP

``````// C++ program to demonstrate working of count()
// and find()
#include <algorithm>
#include <iostream>
#include <vector>
using namespace std;

int main()
{
// Initializing vector with array values
int arr[] = {10, 20, 5, 23 , 42, 20, 15};
int n = sizeof (arr)/ sizeof (arr[0]);
vector< int > vect(arr, arr+n);

cout << "Occurrences of 20 in vector : " ;

// Counts the occurrences of 20 from 1st to
// last element
cout << count(vect.begin(), vect.end(), 20);

// find() returns iterator to last address if
// element not present
find(vect.begin(), vect.end(), 5) != vect.end()?
cout << "\nElement found" :

return 0;
}``````

``````Occurrences of 20 in vector : 2
Element found``````

8.binary_search(first_iterator, last_iterator, x)–测试x是否存在于排序的向量中。

9. lower_bound(first_iterator, last_iterator, x)–返回一个迭代器, 该迭代器指向[first, last)范围内第一个元素, 该元素的值不小于" x"。

10. upper_bound(first_iterator, last_iterator, x)–返回一个迭代器, 该迭代器指向[first, last)范围内第一个元素, 该元素的值大于" x"。

## C ++

``````// C++ program to demonstrate working of lower_bound()
// and upper_bound().
#include <algorithm>
#include <iostream>
#include <vector>
using namespace std;

int main()
{
// Initializing vector with array values
int arr[] = {5, 10, 15, 20, 20, 23, 42, 45};
int n = sizeof (arr)/ sizeof (arr[0]);
vector< int > vect(arr, arr+n);

// Sort the array to make sure that lower_bound()
// and upper_bound() work.
sort(vect.begin(), vect.end());

// Returns the first occurrence of 20
auto q = lower_bound(vect.begin(), vect.end(), 20);

// Returns the last occurrence of 20
auto p = upper_bound(vect.begin(), vect.end(), 20);

cout << "The lower bound is at position: " ;
cout << q-vect.begin() << endl;

cout << "The upper bound is at position: " ;
cout << p-vect.begin() << endl;

return 0;
}``````

``````The lower bound is at position: 3
The upper bound is at position: 5``````

1. arr.erase(要删除的位置)–这将擦除矢量中的选定元素, 并相应地移动和调整矢量元素的大小。
2. arr.erase(唯一(arr.begin(), arr.end()), arr.end())–这会擦除单行中排序向量中的重复出现。

## CPP

``````// C++ program to demonstrate working of erase()
#include <algorithm>
#include <iostream>
#include <vector>
using namespace std;

int main()
{
// Initializing vector with array values
int arr[] = {5, 10, 15, 20, 20, 23, 42, 45};
int n = sizeof (arr)/ sizeof (arr[0]);
vector< int > vect(arr, arr+n);

cout << "Vector is :" ;
for ( int i=0; i<6; i++)
cout << vect[i]<< " " ;

// Delete second element of vector
vect.erase(vect.begin()+1);

cout << "\nVector after erasing the element: " ;
for ( int i=0; i<5; i++)
cout << vect[i] << " " ;

// sorting to enable use of unique()
sort(vect.begin(), vect.end());

cout << "\nVector before removing duplicate "
" occurrences: " ;
for ( int i=0; i<5; i++)
cout << vect[i] << " " ;

// Deletes the duplicate occurrences
vect.erase(unique(vect.begin(), vect.end()), vect.end());

cout << "\nVector after deleting duplicates: " ;
for ( int i=0; i< vect.size(); i++)
cout << vect[i] << " " ;

return 0;
}``````

``````Vector is :5 10 15 20 20 23
Vector after erasing the element: 5 15 20 20 23
Vector before removing duplicate  occurrences: 5 15 20 20 23
Vector after deleting duplicates: 5 15 20 23 42 45``````

3. next_permutation(first_iterator, last_iterator)–这将向量修改为其下一个排列。

4. prev_permutation(first_iterator, last_iterator)–这将向量修改为其先前的排列。

## CPP

``````// C++ program to demonstrate working
// of next_permutation()
// and prev_permutation()
#include <algorithm>
#include <iostream>
#include <vector>
using namespace std;

int main()
{
// Initializing vector with array values
int arr[] = {5, 10, 15, 20, 20, 23, 42, 45};
int n = sizeof (arr)/ sizeof (arr[0]);
vector< int > vect(arr, arr+n);

cout << "Given Vector is:\n" ;
for ( int i=0; i<n; i++)
cout << vect[i] << " " ;

// modifies vector to its next permutation order
next_permutation(vect.begin(), vect.end());
cout << "\nVector after performing
next permutation:\n";
for ( int i=0; i<n; i++)
cout << vect[i] << " " ;

prev_permutation(vect.begin(), vect.end());
cout << "\nVector after performing prev
permutation:\n";
for ( int i=0; i<n; i++)
cout << vect[i] << " " ;

return 0;
}``````

``````Given Vector is:
5 10 15 20 20 23 42 45
Vector after performing next permutation:
5 10 15 20 20 23 45 42
Vector after performing prev permutation:
5 10 15 20 20 23 42 45``````

5.距离(first_iterator, 期望位置)–它返回到第一个迭代器的期望位置的距离。此功能在查找索引时非常有用。

## CPP

``````// C++ program to demonstrate working of distance()
#include <algorithm>
#include <iostream>
#include <vector>
using namespace std;

int main()
{
// Initializing vector with array values
int arr[] = {5, 10, 15, 20, 20, 23, 42, 45};
int n = sizeof (arr)/ sizeof (arr[0]);
vector< int > vect(arr, arr+n);

// Return distance of first to maximum element
cout << "Distance between first to max element: " ;
cout << distance(vect.begin(), max_element(vect.begin(), vect.end()));
return 0;
}``````

``Distance between first to max element: 7``

STL文章

Manjeet Singh。