See this page as a slide show
CS253 Copy If
First attempt
vector<int> foo;
for (int i=1; i<=20; i++)
foo.push_back(rand() % 10);
for (auto v : foo)
cout << v << ' ';
cout << endl;
vector<int> bar;
// copy only odd numbers:
copy_if(foo.begin(), foo.end(), bar.begin(),
[](int i){return i%2;} );
for (auto v : bar)
cout << v << ' ';
3 6 7 5 3 5 6 2 9 1 2 7 0 9 3 6 0 6 2 6
SIGSEGV: Segmentation fault
Second attempt
vector<int> foo;
for (int i=1; i<=20; i++)
foo.push_back(rand() % 10);
for (auto v : foo)
cout << v << ' ';
cout << endl;
vector<int> bar(foo.size());
// copy only odd numbers:
copy_if(foo.begin(), foo.end(), bar.begin(),
[](int i){return i%2;} );
for (auto v : bar)
cout << v << ' ';
3 6 7 5 3 5 6 2 9 1 2 7 0 9 3 6 0 6 2 6
3 7 5 3 5 9 1 7 9 3 0 0 0 0 0 0 0 0 0 0
Third attempt
vector<int> foo;
for (int i=1; i<=20; i++)
foo.push_back(rand() % 10);
for (auto v : foo)
cout << v << ' ';
cout << endl;
vector<int> bar(foo.size());
// copy only odd numbers:
auto it = copy_if(foo.begin(), foo.end(), bar.begin(),
[](int i){return i%2;} );
bar.resize(it-bar.begin());
for (auto v : bar)
cout << v << ' ';
3 6 7 5 3 5 6 2 9 1 2 7 0 9 3 6 0 6 2 6
3 7 5 3 5 9 1 7 9 3
In-place
vector<int> foo;
for (int i=1; i<=20; i++)
foo.push_back(rand() % 10);
for (auto v : foo)
cout << v << ' ';
cout << endl;
// copy only odd numbers:
auto it = copy_if(foo.begin(), foo.end(), foo.begin(),
[](int i){return i%2;} );
foo.resize(it-foo.begin());
for (auto v : foo)
cout << v << ' ';
3 6 7 5 3 5 6 2 9 1 2 7 0 9 3 6 0 6 2 6
3 7 5 3 5 9 1 7 9 3
