C++ Learning Journey Day3

2021-10-03

C++

Symbols count in article: 982 Reading time: 6 mins.

Section 7: Loops

Loops - Iterative Statement

while
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while (<condition>) {
process;
}
do while
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do {
process;
} while (<condition>)

Print the numbers example.

while

int n, i = 1;
cout << "Enter n";
cin >> n;
while (i <= n) {
    cout << i << endl;
    i++;
}

do while

int n, i = 1;
cout << "Enter n";
cin >> n;
do {
    cout << i << endl;
    i++;
} while (i <= n);

for loop

for

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for (initialization; condition; updation) {
  process;
}

Print the numbers example

int n, i;
cout << "Enter n";
cin >> n;
for (i = 1; i <= n; i++) {
    cout << i << endl;
}

for each

Infinite loop

You can skip condition in the for and define the initialization and condition somewhere else.

int i = 0;
for (;;)
{
    cout << i << " Hello\n";
    i++;
    if (i > 10)
        break;
}

Multiplication Table

Example.

int n, i;
cout << "Enter n";
cin >> n;
for (i = 1; i <= 10; i++) {
    cout << n << " x " << i << " = " << n * i << endl;
}

Find GDC of 2 numbers

Example.

int m, n;
cout << "Enter 2 numbers";
cin >> m >> n;
while (m != n) {
    if (m > n)
        m -= n;
    else
        n -= m;
}
cout << "GCD is " << m << endl;

Section 8: Array

Introduction

Array can be any type, such as int, float, char.

Declaration:

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int A[5] = {2, 4, 6, 8, 10};
float B[5] = {1.1, 2.4, 3.7, 6.2, 9.5};
char C[5] = {'A', 'B', 'C', 'D', 'E'};

You can initialize without assigning data, it will be 0. And you can initialize without length, it will give it a size automatically.
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int A[5] = {2, 4}; // A = {2, 4, 0, 0, 0};
int B[] = {1, 2, 4, 6} // B = {1, 2, 4, 6};

Array Declarations

Declare the array without initialization.

int A[5];
for (int i = 0; i < 5; i++)
    cout << A[i] << endl;
====OUTPUT====
0
0
0
0
-487864256

If you assign more data than array length, it will have the compile error. For example, int A[5] = {2, 4, 6, 8, 10, 12};.

For each loop.

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int A[6] = {2, 4, 6, 8, 10, 12};
for (int x : A)
    cout << x << endl;

You can use auto to specify the type automatically.

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float A[] = {2.5f, 5.6f, 9, 8, 7};
for (auto x : A)
    cout << x << endl;

If you don’t want to specify automatically, you can specify the type by yourself. For example, you can specify int to read char, it will show the ASCII code of char.

char A[] = {'A', 66, 'C', 68};
for (auto x : A)
    cout << x << endl;
====OUTPUT====
A
B
C
D

char A[] = {'A', 66, 'C', 68};
for (int x : A)
    cout << x << endl;
====OUTPUT====
65
66
67
68

For Each loop

You can use pointer to change the original value in the array by for each loop.
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int A[] = {8, 6, 3, 9, 7, 4};
for (auto &x : A)
cout << ++x << endl;

Nested Loops

If you want to working on matrixes, it will use nested loops. For example.

for (int i = 0; i < 3; i++) {
    for (int j = 0; j < 3; j++) {
        cout << i << j << endl;
    }
}

Multidimensional Array

Multidimensional array can initialize may ways. If you don’t specify the value, it will be zero.
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int A[2][3] = { {2, 5, 9}, {6, 9, 15} };
int A[2][3] = {2, 5, 9, 6, 9, 15};
int A[2][3] = {2, 5}

print all value in the multidimensional array.

int A[3][4] = { {2, 5, 9}, {6, 9, 15} };

for (int i = 0; i < 2; i++) {
    for (int j = 0; j < 3; j++) {
        cout << A[i][j] << " ";
    }
    cout << endl;
}

Use for each to print out the multidimensional array.

int A[2][3] = {2, 4, 6, 3, 5, 7};

for (auto& x : A) {
    for (auto& y : x) {
        cout << y << " ";
    }
    cout << endl;
}

Add two matrixes.

int A[2][3] = { {2, 5, 9}, {7, 3, 6} };
int B[2][3] = { {6, 3, 4}, {9, 5, 2} };
int C[2][3];
for (int i = 0; i < 2; i++) {
    for (int j = 0; j < 3; j++) {
        C[i][j] = A[i][j] + B[i][j];
    }
}

for (int i = 0; i < 2; i++) {
    for (int j = 0; j < 3; j++) {
        cout << C[i][j] << " ";
    }
    cout << endl;
}

Disclaimer

I took this course from Udemy, which is Learn C++ Programming -Beginner to Advance- Deep Dive in C++. I only took some notes of this amazing course for my personal future uses and share my thoughts with my peers. If you like it, you should take the course from Udemy too.

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