Lecture 2: Dynamic Allocation

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Lecture 2: Dynamic Allocation START HERE

Lecture 2: Dynamic Allocation

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//============>>>>>>>>>> Lecture 2: Dynamic Allocation Notes

Lecture 2: Dynamic Allocation Notes.pdf

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Address Typecasting

#include <iostream>
using namespace std;

int main() {
    int i = 65;
    char c = i;
    cout << c << endl;

    int * p = &i;
    char * pc = (char*)p;

    cout << p << endl;
    cout << pc << endl;

    cout << *p << endl;
    cout << *pc << endl;
    cout << *(pc + 1) << endl;
    cout << *(pc + 2) << endl;
    cout << *(pc + 3) << endl;
}

//output
A
0x7fff5d63d384
A
65
A
�
�
�

Reference and Pass By Reference

#include <iostream>
using namespace std;

void increment(int& i) {
    i++;
}

// bad practice
int& f(int n) {
    int a = n;
    return a;
}

// bad practice
int* f2() {
    int i = 10;
    return &i;
}

int main() {
    int* p = f2();

    int i;
    i = 10;

    int& k1 = f(i);

    increment(i);
    cout << i << endl;

    int& j = i;

    i++;
    cout << j << endl;
    j++;
    cout << i << endl;

    int k = 100;
    j = k;
    cout << i << endl;
}

//output
11
12
13
100

Dynamic Memory Allocation

#include <iostream>
using namespace std;

int main() {

    int *p = new int;
    delete p;

    p = new int;
    delete p;

    p = new int[100];
    delete [] p;

    /*
    while (true) {
        int *p = new int;
    }

    while (true) {
        int i = 10;
    }
*/

}

#include <iostream>
using namespace std;

int main() {
    int * p = new int;
    *p = 10;
    cout << *p << endl;

    double *pd = new double;

    char* c = new char;

    int* pa = new int[50];
    int n;
    cout << "Enter num of elements" << endl; 
    cin >> n;

    int* pa2 = new int[n];
    for (int i = 0; i < n; i++) {
        cin >> pa2[i];
    }

    int max = -1;
    for (int i = 0; i < n; i++) {
        if (max < a[i]) {
            max = a[i];
        }
    }
    cout << max << endl;
}

Dynamic Allocation of 2D Arrays

#include <iostream>
using namespace std;

int main() {
    int m, n;
    cin >> m >> n;
    int** p = new int*[m];
    for (int i = 0; i < m; i++) {
        p[i] = new int[i + 1];
        for (int j = 0;j <n; j++) {
            cin >> p[i][j];
        }
    }

    for (int i = 0; i < m; i++) {
        delete [] p[i];
    }
    delete [] p;
}

Macros and Global Variables

/*---------------Macros-----------*/
#include <iostream>
using namespace std;

int a;

void g() {
    a++;
    cout << a << endl;
}

void f() {
    cout << a << endl;
    a++;
    g();
}

int main() {
    a = 10;
    f();
    f();
    cout << a << endl;
}

/*-------------------define------------*/
#include <iostream>
using namespace std;
#define PI 3.14

int main() {

    int r;
    cin >> r;

    cout << PI * r * r << endl;

}

Inline and Default Arguments

/*-----------------default_arguments.cpp-----*/
#include <iostream>
using namespace std;

int sum(int a[], int size, int si = 0) {
    int ans = 0;
    for (int i = si; i < size; i++) {
        ans += a[i];
    }
    return ans;
}

int sum2(int a, int b = 0, int c = 0, int d = 0) {
    return a + b + c + d;
}

int main() {
     int a[20];
     // input code for a

     cout << sum(a, 20) << endl;
}

/*---------inline.cpp-----------*/
#include <iostream>
using namespace std;

inline int max(int a, int b) {
    return (a > b)?  a : b;
}

int main() {
    int a, b;
    cin >> a >> b;

    int c = max(a, b);

    int x,y;
    x = 12;
    y = 34;

    int z = max(x, y);
}

Constant Variables

/*-------------CONST POINTER------------*/
#include <iostream>
using namespace std;

int main() {
    int i = 10;
    int j = 21;
    int const * p = &i;

    p = &j;

    int * const p2 = &i;
    (*p2)++;
    //p2 = &j;

    int const * const p3 = &i;
    p3 = &j;
    (*p3)++;
}

/*-------------CONST POINTER------------*/
#include <iostream>
using namespace std;

void g(int const & a) {
    a++;
}

void f(const int * p) {
}

int main() {
    int const i = 10;
    int const * p = &i;

    int j = 12;
    int* p3 = &j;
    f(p3);
    g(j);

    int const * p2 = &j;
    cout << *p2 << endl;
    j++;
    cout << *p2 << endl;
}

/*-------------CONST REFFERENCE------------*/
#include <iostream>
using namespace std;

int main() {
    // constant int
    const int i = 10;
    int const i2 = 10;

    // constant reference from a non const int
    int j = 12;
    const int & k = j;
    j++;

    cout << k << endl;

    // constant reference from a const int
    int const j2 = 12;
    int const &k2 = j2;

    // reference from a const int
    int const j3 = 123;
    int & k3 = j3;
    k3++;
}

QUIZZZ

Lecture 2: Dynamic Allocation END HERE