一、STL中的算法
- sort(first_iterator, last_iterator) – To sort the given vector.
- reverse(first_iterator, last_iterator) – To reverse a vector.
- max_element (first_iterator, last_iterator) – To find the maximum element of a vector.
- ***min_element (first_iterator, last_iterator) **– To find the minimum element of a vector.
- accumulate(first_iterator, last_iterator, initial value of sum) – Does the summation of vector elements
// A C++ program to demonstrate working of sort(),
// reverse()
#include
#include
#include
#include //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 vect(arr, arr+n);
cout << "Vector is: ";
for (int i=0; i 重要！！！
- count(first_iterator, last_iterator,x) – To count the occurrences of x in vector.
7. find(first_iterator, last_iterator, x) – Points to last address of vector ((name_of_vector).end()) if element is not present in vector.
// C++ program to demonstrate working of count()
// and find()
#include
#include
#include
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 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":
cout << "\nElement not found";
return 0;
}
- binary_search(first_iterator, last_iterator, x) – Tests whether x exists in sorted vector or not.
- lower_bound(first_iterator, last_iterator, x) – returns an iterator pointing to the first element in the range [first,last) which has a value not less than ‘x’.
- upper_bound(first_iterator, last_iterator, x) – returns an iterator pointing to the first element in the range [first,last) which has a value greater than ‘x’.
// C++ program to demonstrate working of lower_bound()
// and upper_bound().
#include
#include
#include
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 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;
}
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- arr.erase(position to be deleted) – This erases selected element in vector and shifts and resizes the vector elements accordingly.
- arr.erase(unique(arr.begin(),arr.end()),arr.end()) – This erases the duplicate occurrences in sorted vector in a single line
// C++ program to demonstrate working of erase()
#include
#include
#include
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 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;
}
image.png