How should i use remove_if to delete elements in range of two numbers

Question

I created Class and initialised a vector inside private field, then i initialised vector by useing methods of my Class. Now i need to delete elements in range of two numbers which i have to type on a keyboard

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

int randomNumber()
{
    return (0 + rand() % 50 - 10);
}

class Array {
vector<int>::iterator p;
public:
    vector<int>array;
    Array(int size)
    {
        array.resize(size);
        generate(array.begin(), array.end(), randomNumber);
    }
    void Print() {
        for (p = array.begin(); p != array.end(); p++) {
            cout << *p << ' ';
        }
        cout << endl;
    }
    void Condense() {
        int a, b;
        cout << "Enter your range: [";  
        cin >> a;
        cin >> b;
        cout << "]" << endl;
        for (p = array.begin(); p != array.end(); p++) {
            if (a < *p < b || a > *p < b) {

            }
        }
    }
};

not an answer, but why do you insert the unwanted elements to the vector in the first place? Wouldnt it be easier to first ask the user for the range and only then insert numbers into the vector? — 463035818_is_not_an_ai, Oct 07 '19 at 10:00
is `generate` `std::generate` ? Do you have a `using namespace std;` in your real code? In any case `array` is not a good name for a variable — 463035818_is_not_an_ai, Oct 07 '19 at 10:01
https://stackoverflow.com/questions/1452721/why-is-using-namespace-std-considered-bad-practice — 463035818_is_not_an_ai, Oct 07 '19 at 10:02
please make sure the code you post is complete and has no errors unrelated to your question. The one you posted wont compile with a wall of errors (that should be easy to fix) — 463035818_is_not_an_ai, Oct 07 '19 at 10:06

Vlad from Moscow · Accepted Answer · 2019-10-07T10:35:59.513

Here is a demonstrative program that shows how you can remove elements of a vector in the range ( a, b ).

#include <iostream>
#include <vector>
#include <tuple>
#include <iterator>
#include <algorithm>

int main() 
{
    std::vector<int> v = { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 };

    for ( const auto &item : v ) std::cout << item << ' ';
    std::cout << '\n';

    int a = 7, b = 2;

    std::tie( a, b ) = std::minmax( { a, b } );

    auto inside_range = [&]( const auto &item )
    {
        return a < item && item < b;
    };

    v.erase( std::remove_if( std::begin( v ), std::end( v ), inside_range ),
             std::end( v ) );

    for ( const auto &item : v ) std::cout << item << ' ';
    std::cout << '\n';

    return 0;
}

Its output is

0 1 2 3 4 5 6 7 8 9 
0 1 2 7 8 9

Instead of using std::minmax and std::tie to order a and b you could just write the condition like

    auto inside_range = [&]( const auto &item )
    {
        return a < item && item < b || b < item && item < a;
    };

As for your code then the condition in the if statement

if ( a < *p < b || a > *p < b) {

is incorrect, You mean

if (a < *p && *p < b || b < *p && *p < a ) {

How should i use remove_if to delete elements in range of two numbers

1 Answers1