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#include <iostream>
#include <algorithm>
#include <vector>
using namespace std;
// cout << "compare " << vectEl.val << ", " <<
// vectEl.ch << " to " <<
// value.val << ", " << value.ch << '\n';
int main()
{
struct X
{
int val;
char ch;
};
// lambda expression:
// 1st parameter: fixed value,
// 2nd parameter: element from the vector.
//
// sorted in ascending order: use 2nd-param. < 1st-param or
// 2nd-param <= 2nd-param
//
// If the value to sort with (= the key) is not present in the
// sorted vector then all variants (upper_bound, lower_bound,
// using > or >= when descendingly sorted, using < or <= when
// ascendingly sorted return the iterator to the positing where
// the key should be inserted.
//
// If the value to sort with (= the key) already is present in the
// sorted vector then:
// * lower_bound with <= and upper_bound with < return the
// iterator to the first occurrence of the key in the sorted
// vector;
// * lower_bound with < and upper_bound with <= return the
// iterator beyond the last occurrence of the key in the sorted
// vector
//
// sorted in descending order: use 2nd-param. > 1st-param or
// 2nd-param >= 2nd-param
//
// If the value to sort with (= the key) already is present in the
// sorted vector then:
// * lower_bound with >= and upper_bound with > return the
// iterator to the first occurrence of the key in the sorted
// vector;
// * lower_bound with > and upper_bound with >= return the
// iterator beyond the last occurrence of the key in the sorted
// vector
{
vector<X> values
{
{ 4, 'X' },
{ 1, 'a' },
{ 2, 'a' },
{ 3, 'a' },
{ 4, 'b' },
{ 4, 'c' },
{ 5, 'a' },
{ 7, 'a' },
{ 9, 'a' }
};
// UPDATE THE ABOVE TEXT ACCORDING TO THIS:
// note that the 1st param. refers to the vector, the 2nd to the value
// auto insert = upper_bound(
auto insert = lower_bound(
values.begin() + 1, values.end(),
values[0],
[&](X const &vectEl, X const &value)
{
return vectEl.val <= value.val;
// upper_bound: with <= at the beginning, lower_bound with <
// upper_bound: with < at the end, lower_bound with <=
}
);
cout << "FIRST Insert at " << (insert - values.begin()) << '\n';
// insert points at the 1st element <= value: the topmost
// element should be moved there.
rotate(values.begin(), values.begin() + 1, insert);
for (X const &value: values)
cout << value.val << ' ' << value.ch << ", ";
// upper_bound: 1 a, 2 a, 3 a, 4 X, 4 b, 4 c, 5 a, 7 a, 9 a,
// or lower-bound with <=
// lower bound: 1 a, 2 a, 3 a, 4 b, 4 c, 4 X, 5 a, 7 a, 9 a,
// or upper_bound with <=
cout << '\n';
}
{
vector<X> values
{
{ 4, 'X' },
{ 9, 'a' },
{ 7, 'a' },
{ 5, 'a' },
{ 4, 'b' },
{ 4, 'c' },
{ 3, 'a' },
{ 2, 'a' },
{ 1, 'a' }
};
// auto insert = upper_bound(
auto insert = lower_bound(
values.begin() + 1, values.end(),
values[0],
[&](X const &vectEl, X const &value)
{
return vectEl.val >= value.val;
}
);
// upper_bound: with >= at the beginning, lower_bound with >
// upper_bound: with > at the end, lower_bound with >=
cout << "FIRST: Insert at " << (insert - values.begin()) << '\n';
// insert points at the 1st element <= value: the topmost
// element should be moved there.
rotate(values.begin(), values.begin() + 1, insert);
for (X const &value: values)
cout << value.val << ' ' << value.ch << ", ";
// upper_bound: 9 a, 7 a, 5 a, 4 X, 4 b, 4 c, 3 a, 2 a, 1 a,
// or lower_bound with >=
// lower bound: 9 a, 7 a, 5 a, 4 b, 4 c, 4 X, 3 a, 2 a, 1 a,
// or upper_bound with >=
cout << '\n';
}
return 0;
{
vector<X> values
{
{ 4, 'X' },
{ 9, 'a' },
{ 7, 'a' },
{ 5, 'a' },
{ 3, 'a' },
{ 2, 'a' },
{ 1, 'a' }
};
auto insert = lower_bound(
values.rbegin(), values.rend() - 1,
values[0],
[&](X const &value, X const &vectEl)
{
return vectEl.val >= value.val;
}
);
cout << "Insert at " << (insert.base() - values.begin()) << '\n';
// insert points at the 1st element <= value: the topmost
// element should be moved there.
rotate(values.begin(), values.begin() + 1, insert.base());
for (X const &value: values)
cout << value.val << ' ' << value.ch << ", ";
// all variants (upper_bound, lower_bound, >, >= :
// 9 a, 7 a, 5 a, 4 X, 3 a, 2 a, 1 a,
cout << '\n';
}
}
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