Standard Library Sequence Reordering Algorithms Sequence Reordering Algorithms Reorder

#include <vector>
#include <iostream>
#include <algorithm>

int main () {
std::vector<int> v {0,1,2,4,6,8,9,3,5};
// reverse subrange (as shown in image):
reverse(begin(v)+2, begin(v)+7);  
for (int x : v) { std::cout << x << ' '; }  // 0 1 9 8 6 4 2 3 5
std::cout << '\n';
// reverse entire vector:
reverse(begin(v), end(v));  
for (int x : v) { std::cout << x << ' '; }  // 5 3 2 4 6 8 9 1 0
std::cout << '\n';
}

#include <vector>
#include <iostream>
#include <algorithm>

int main () {
std::vector<int> in {0,1,2,4,6,8,9,3,5};
std::vector<int> out; 
out.resize(5);
reverse_copy(begin(in)+2, begin(in)+7, begin(out));
for (int x : out) { std::cout << x << ' '; }  // 9 8 6 4 2
std::cout << '\n';
}

#include <vector>
#include <iostream>
#include <algorithm>

int main () {
std::vector<int> v {1,2,3,4,5,6,7};
auto i = rotate(begin(v), begin(v)+2, end(v));  
for (int x : v) { std::cout << x <<' '; }  // 3 4 5 6 7 1 2
std::cout << '\n';
// returned iterator refers to old first:
auto const value = *i;  // 1
auto const index = distance(begin(v), i);  // 5
std::cout << "value: " << value << '\n';
std::cout << "index: " << index << '\n';
}

#include <vector>
#include <iostream>
#include <algorithm>

int main () {
std::vector<int> in {1,2,3,4,5,6,7};
std::vector<int> out; 
out.resize(in.size());
rotate_copy(begin(in), begin(in)+2,             end(in), begin(out));  
for (int x : out) { std::cout << x <<' '; }  // 3 4 5 6 7 1 2
std::cout << '\n';
}

#include <vector>
#include <iostream>
#include <algorithm>
#include <random>

int main () {
// 32 bit mersenne twister engine
auto const seed = std::random_device{}();
auto reng = std::mt19937{seed};
std::vector<int> v {0,1,2,3,4,5,6,7,8};
shuffle(begin(v)+2, begin(v)+7, reng);  
for (int x : v) { std::cout << x <<' '; }  // 0 1 … 7 8
std::cout << '\n';
}

#include <vector>
#include <iostream>
#include <algorithm>

int main () {
std::vector<int> v {8,9,3,1,2,3,5,4,7,6};
// sort subrange (as shown in image):
sort(begin(v)+2, begin(v)+8);
for (int x : v) { std::cout << x <<' '; }  // 8 9 1 2 3 3 4 5 7 6
std::cout << '\n';

// sort entire vector:
sort(begin(v), end(v));
for (int x : v) { std::cout << x <<' '; }  // 1 2 3 3 4 5 6 7 8 9
std::cout << '\n';

// sort vector in descending order:
sort(begin(v), end(v), std::greater<>{});
for (int x : v) { std::cout << x <<' '; }  // 9 8 7 6 5 4 3 3 2 1
std::cout << '\n';
}

#include <vector>
#include <iostream>
#include <algorithm>

int main () {
std::vector<int> range {3,1,2,3,5,4};
std::ranges::sort(range);
for (int x : range) { std::cout << x <<' '; }  // 1 2 3 3 4 5
std::cout << '\n';

// sort in descending order:
std::ranges::sort(range, std::greater<>{});
for (int x : range) { std::cout << x <<' '; }  // 5 4 3 3 2 1
std::cout << '\n';
}

#include <vector>
#include <iostream>
#include <algorithm>

int main () {
std::vector<int> v {4,2,5,6,3,7,1};
// get 5th element in sorted order
int const n = 4;
auto nth = begin(v) + n;
nth_element(begin(v), nth, end(v));
std::cout << *nth;  // 5
std::cout << '\n';
}

#include <vector>
#include <iostream>
#include <algorithm>

int main () {
auto const is_odd = [](int x) {   return (x & 1); };
std::vector<int> v {3,4,6,5,7,8,0};
auto i = partition(begin(v), end(v), is_odd);
auto const print = [](int x){ std::cout << x << ' '; };
// print 1st subrange
std::for_each(begin(v), i, print);  // 3 7 5
std::cout << '\n';
// print 2nd subrange
std::for_each(i, end(v), print);  // 6 4 8 0
std::cout << '\n';
}

#include <vector>
#include <iostream>
#include <algorithm>

int main () {
auto const is_odd = [](int x) {   return (x & 1); };
std::vector<int> in {3,4,6,5,0};
// ensure each output could hold all elements:
std::vector<int> out1; out1.resize(in.size());
std::vector<int> out2; out2.resize(in.size());
auto ends = partition_copy(begin(in), end(in), begin(out1), begin(out2), is_odd);
// resize partitions to fit content
out1.erase(ends.first,  end(out1));
out2.erase(ends.second, end(out2));
// print partitions
for (int x : out1) { std::cout << x << ' '; }  // 3 5
std::cout << '\n';
for (int x : out2) { std::cout << x << ' '; }  // 4 6 0
std::cout << '\n';
}