How to use vector in c++

Question

1.00/5 (1 vote)

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Hey,
I'm working on vector in c++, and i really don't understand vector very well
i would like to display the following in the terminal

[]
[0 0 0]
error message
error message
[1 2 3]
[1 2 3 ]
[1 0 3 }

here's my Vector.cpp file

C++

#include "Vector.h"
#include <iostream>
#include <vector>

using namespace std;
int main() {

	vector<double> a, b(3), c(3);

a.print ();   //outputs []
b.print ();   // outputs [0 0 0]
c.set(0,-1):   //output error message
c.set(1,0):
c.set(2,1):
c.set(3,2):
c.set(4,3):         /output error message
c.print();           //output [1 2 3]

vector d(c);     
d.print();           //outputs [1 2 3 ] 

d.set(0,1);   
d.print();         // outputs [1 0  3 }

return 0 ; 
}

and here's my Vector.h file

C++

#ifndef VECTOR_H
#define VECTOR_H
#define NULL 0
#include <iostream>

using namespace std;
class Vector
{
public:
	Vector::Vector() {
		size = 0;
		enteries = new int[size];
		for (int k = 0; k < size; k++) {

			enteries[k] = 0;
		}
	}
	Vector::Vector(int s) {
		size = s;
		enteries = new int[size];
		for (int L = 0; L < size; L++) {
			enteries[L] = 0;
		}
	}

	Vector::Vector(const Vector & other) {
		this->size = other.size;
		this->enteries = new int[size];
		for (int i = 0; i < size; i++) {

			this->enteries[i] = other.enteries[i];
		}
	}

	Vector::~Vector() {
		this->enteries = NULL;
	}
	void Vector::print() {
		cout << endl << "[";
		for (int i = 0; i < size; i++) {
			cout << enteries[i] << " ";
		}
		cout << "]" << endl;
	}
	void Vector::set(int val, int pos) {
		if (pos < 0|| pos < size) {
			cout << endl << "Error Message ";
		}
	}


private:
	int size; 
	int *enteries; 
};
#endif

What I have tried:

I have already did the header file, but i really don't know how to display the following after running the program
[]
[0 0 0]
error message
error message
[1 2 3]
[1 2 3 ]
[1 0 3 }
Thank you for your help.

Posted 16-Feb-16 4:30am

Assam ALzookery

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Comments

Sergey Alexandrovich Kryukov 16-Feb-16 11:11am

And the problem is..?
—SA

Assam ALzookery 16-Feb-16 11:16am

i don't know how to finish cpp file to get the result
Thank you

Philippe Mori 16-Feb-16 12:31pm

Use a debugger. Don't reinvent the wheel and use std::vector instead!

2 solutions

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Jochen Arndt · Accepted Answer · 2016-02-16T05:27:00

The size checking in set() is wrong and you are not assigning the value:

C++

void Vector::set(int val, int pos) {
    // This is wrong:
    //if (pos < 0|| pos < size) {
    // It should be:
    if (pos < 0 || pos >= size) {
        cout << endl << "Error Message ";
    }
    // This is missing:
    else
        enteries[pos] = val;
}

In your destructor you should delete the allocated memory. Setting the pointer to NULL is useless:

Vector::~Vector() {
    // This is missing:
    delete [] this->enteries;
    // This is useless:
    //this->enteries = NULL;
}

nv3 · Accepted Answer · 2016-02-16T08:26:00

Solution 2

And in addition to solution 1: If you define Vector in your header file you should use Vector in your cpp file (note the capital V), and not vector!

Posted 16-Feb-16 8:26am

nv3