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C++ Algorithm rotate()C++ Algorithm rotate() function is used to rotate the order of the elements within a range [first, last).
Syntaxtemplate <class ForwardIterator> void rotate (ForwardIterator first, ForwardIterator middle, ForwardIterator last); // until C++ 11 template <class ForwardIterator> ForwardIterator rotate (ForwardIterator first, ForwardIterator middle, ForwardIterator last); //since C++ 11 Parameterfirst: A forward iterator pointing the position of the first element in the range to be rotated. middle: A forward iterator addressing to the element within the range [first, last) that is moved to the first position in the range. last: A forward iterator pointing the position one past the final element in the range in which the elements are being reversed. Return valueNone ComplexityComplexity is linear in the range [first, last): swaps or moves elements until all elements have been relocated. Data racesThe object in the range [first, last) are modified. ExceptionsThis function throws an exception if either an element swap or move or an operation on iterator throws an exception. Please note that invalid parameters cause an undefined behavior. Example 1Let's see the simple example to rotate the given string: #include <algorithm> #include <iostream> #include <string> using namespace std; int main() { string str = "Hello"; cout << "Before Rotate : "<< str << endl; rotate(str.begin(), str.begin() + 2, str.end()); cout <<"After Rotate : " << str << endl; return 0; } Output: Before Rotate : Hello After Rotate : lloHe Example 2Let's see another simple example: #include <iostream> #include <algorithm> #include <vector> #include <iomanip> using namespace std; void print(char a[], int N) { for(int i = 0; i < N; i++) { cout << (i + 1) << ". " << setw(2) << left << a[i] << " "; } cout << endl; } int main() { char s[] = {'A', 'B', 'C', 'D', 'E', 'G', 'H'}; int slen = sizeof(s) / sizeof(char); cout << "Original order : "; print(s, slen); cout << "Rotate with \'C\' as middle element" << endl; rotate(s, s + 2, s + slen); cout << "Rotated order : "; print(s, slen); cout << "Rotate with \'G\' as middle element" << endl; rotate(s, s + 3, s + slen); cout << "Rotated order : "; print(s, slen); cout << "Rotate with \'A\' as middle element" << endl; rotate(s, s + 3, s + slen); cout << "Original order : "; print(s, slen); return 0; } Output: Original order : 1. A 2. B 3. C 4. D 5. E 6. G 7. H Rotate with 'C' as middle element Rotated order : 1. C 2. D 3. E 4. G 5. H 6. A 7. B Rotate with 'G' as middle element Rotated order : 1. G 2. H 3. A 4. B 5. C 6. D 7. E Rotate with 'A' as middle element Original order : 1. B 2. C 3. D 4. E 5. G 6. H 7. A Example 3Let's see another simple example: #include<iostream> #include<algorithm> #include<vector> using namespace std; int main () { vector<int> vec1{1,2,3,4,5,6,7,8,9}; // Print old vector cout << "Old vector:"; for(int i=0; i < vec1.size(); i++) cout << " " << vec1[i]; cout << "\n"; // Rotate vector left 3 times. int rotL=3; // rotate function rotate(vec1.begin(), vec1.begin()+rotL, vec1.end()); // Print new vector cout << "New vector after left rotation :"; for (int i=0; i < vec1.size(); i++) cout<<" "<<vec1[i]; cout << "\n\n"; vector <int> vec2{1,2,3,4,5,6,7,8,9}; // Print old vector cout << "Old vector:"; for (int i=0; i < vec2.size(); i++) cout << " " << vec2[i]; cout << "\n"; // Rotate vector right 4 times. int rotR = 4; // std::rotate function rotate(vec2.begin(), vec2.begin()+vec2.size()-rotR, vec2.end()); // Print new vector cout << "New vector after right rotation :"; for (int i=0; i < vec2.size(); i++) cout << " " << vec2[i]; cout << "\n"; return 0; } Output: Old vector : 1 2 3 4 5 6 7 8 9 New vector after left rotation : 4 5 6 7 8 9 1 2 3 Old vector : 1 2 3 4 5 6 7 8 9 New vector after right rotation : 6 7 8 9 1 2 3 4 5 Example 4Let's see another simple example: #include <vector> #include <deque> #include <algorithm> #include <iostream> int main( ) { using namespace std; vector <int> v1; deque <int> d1; vector <int>::iterator v1Iter1; deque<int>::iterator d1Iter1; int i; for ( i = -3 ; i <= 5 ; i++ ) { v1.push_back( i ); } int ii; for ( ii =0 ; ii <= 5 ; ii++ ) { d1.push_back( ii ); } cout << "Vector v1 is ( " ; for ( v1Iter1 = v1.begin( ) ; v1Iter1 != v1.end( ) ;v1Iter1 ++ ) cout << *v1Iter1 << " "; cout << ")." << endl; rotate ( v1.begin ( ) , v1.begin ( ) + 3 , v1.end ( ) ); cout << "After rotating, vector v1 is ( " ; for ( v1Iter1 = v1.begin( ) ; v1Iter1 != v1.end( ) ;v1Iter1 ++ ) cout << *v1Iter1 << " "; cout << ")." << endl; cout << "The original deque d1 is ( " ; for ( d1Iter1 = d1.begin( ) ; d1Iter1 != d1.end( ) ;d1Iter1 ++ ) cout << *d1Iter1 << " "; cout << ")." << endl; int iii = 1; while ( iii <= d1.end ( ) - d1.begin ( ) ) { rotate ( d1.begin ( ) , d1.begin ( ) + 1 , d1.end ( ) ); cout << "After the rotation of a single deque element to the back,\n d1 is ( " ; for ( d1Iter1 = d1.begin( ) ; d1Iter1 != d1.end( ) ;d1Iter1 ++ ) cout << *d1Iter1 << " "; cout << ")." << endl; iii++; } } Output: Vector v1 is ( -3 -2 -1 0 1 2 3 4 5 ). After rotating, vector v1 is ( 0 1 2 3 4 5 -3 -2 -1 ). The original deque d1 is ( 0 1 2 3 4 5 ). After the rotation of a single deque element to the back, d1 is ( 1 2 3 4 5 0 ). After the rotation of a single deque element to the back, d1 is ( 2 3 4 5 0 1 ). After the rotation of a single deque element to the back, d1 is ( 3 4 5 0 1 2 ). After the rotation of a single deque element to the back, d1 is ( 4 5 0 1 2 3 ). After the rotation of a single deque element to the back, d1 is ( 5 0 1 2 3 4 ). After the rotation of a single deque element to the back, d1 is ( 0 1 2 3 4 5 ).
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