: Converting Decimals to Hexadecimals,” gives a program that converts a decimal to a hexadecimal. How do you convert a hex number into a decimal?

#include <iostream>
#include<cmath>
#include<ctime>
#include<string>
#include <iomanip>
#include <fstream>

using namespace std;




void decToBinary(int n)
{
    // array to store binary number 
    int binaryNum[3][3];
    
    //converting to binary 
    for (int i = 0; i < 3; i++) 
    {
        for (int j = 0; j < 3; j++)
        {
            binaryNum[i][j] = n % 2;
            n = n / 2;

        }
     }       

    // printing binary> array in reverse order 
    for (int i = 3-1; i >= 0; i--){
        for (int j = 3 - 1; j >= 0; j--)
        {
            if (binaryNum[i][j] == 0)
                cout << "H" << " ";
            else
                cout << "T" << " ";
        }
        cout << endl;
    }
    
 }

int main()
{
    int n;
    cout << "Enter a decimal number between 1 and 512 ";
    cin >> n;

    decToBinary(n);
    return 0;
}

#include<iostream>
using namespace std;

int sum(int arr[], int a);

int main() {
    int arr[1000], n;
    cin >> n;
    for (int i = 0; i < n; ++i) {
        cin >> arr[i];
        cout << sum(arr, n);
    }
}
int sum(int arr[], int a) {
    int i;
    sum = 0;
    for (i=0; i<n; ++i) {
        sum += arr[i];
    }
    return sum;
}#include<iostream>
using namespace std;

int sum(int arr[], int a);

int main() {
    int arr[1000], n;
    cin >> n;
    for (int i = 0; i < n; ++i) {
        cin >> arr[i];
        cout << sum(arr, n);
    }
}
int sum(int arr[], int a) {
    int i;
    sum = 0;
    for (i=0; i<n; ++i) {
        sum += arr[i];
    }
    return sum;
}

int maxSubArraySum(int a[], int size) 
{ 
int max_so_far = 0, max_ending_here = 0; 
for (int i = 0; i < size; i++) 
{ 
	max_ending_here = max_ending_here + a[i]; 
	if (max_ending_here < 0) 
		max_ending_here = 0; 

	/* Do not compare for all elements. Compare only 
		when max_ending_here > 0 */
	else if (max_so_far < max_ending_here) 
		max_so_far = max_ending_here; 
} 
return max_so_far; 
} 

Part 1:

// Header.h
void func(); // Declares func()
 
// File1.cc
#include "Header.h"
void func() {   // Defines func()
   ...
}
 
// File2.cc
#include "Header.h"
...  // Do something else
func(); // Calls func()
  
  
  
  
  
  
Part 2:

// Header.h
inline void func() { // Defines func()
   ...
}
 
// File2.cc
#include "Header.h"
... // Do something else
... // Code for func()

bool operator<(const Person &other) const {
 if (name == other.name) { 
    return age < other.age;
 } else { 
        return name < other.name; 
    }
} 
 
//This fixes the problem: In template: invalid operands to binary     expression ('const Person' and 'const Person')

std::string test1 = "Baked";
std::string test2 = "Bake";  
bool compare = test1 < test2;
 
// Output: 0
/* Reason: There is no difference until the last letter so then it will compare the last letter with the blank space. 
Since blank space comes first before the letter d, this means that test1 is not less than test2 and that is why it returns false.*/
 
std::string test1 = "Baker";
std::string test2 = "Bdke";  
bool compare = test1 < test2;
 
// Output: 1
/* Reason: There is no difference until the second letter so then it will compare the second letter with the second letter of the other word.
Since the letter a comes first before the letter d, this means that test1 is less than test2 and that is why it returns true.*/

Example:

    people[0] = Person(3, "Bob");
    people[1] = Person(4, "Joe");
    people[2] = Person(5, "Sue");

Example 2:

	people.insert(std::pair <int, Person> (0, Person(3, "Bob")));
	people.insert(std::pair <int, Person> (1, Person(4, "Joe")));
	people.insert(std::pair <int, Person> (2, Person(5, "Sue")));

#include <iostream>

using namespace std;

struct student
{
	int age;
};

int main() {
	student steve;		//variable
	student *ken;		//ken is a pointer.  It points to the memory address which holds the ken struct.

	steve.age = 7;
	ken->age = 9;

	return;
}

#include <iostream>

using namespace std;

int main(){
  	
	cout << "Hello World";
  
  	return 0;
}

std::exception <exception> interface (debatable if you should catch this)
    std::bad_alloc <new> failure to allocate storage
        std::bad_array_new_length <new> invalid array length
    std::bad_cast <typeinfo> execution of an invalid dynamic-cast
    std::bad_exception <exception> signifies an incorrect exception was thrown
    std::bad_function_call <functional> thrown by "null" std::function
    std::bad_typeid <typeinfo> using typeinfo on a null pointer
    std::bad_weak_ptr <memory> constructing a shared_ptr from a bad weak_ptr
    std::logic_error <stdexcept> errors detectable before the program executes
        std::domain_error <stdexcept> parameter outside the valid range
        std::future_error <future> violated a std::promise/std::future condition
        std::invalid_argument <stdexcept> invalid argument
        std::length_error <stdexcept> length exceeds its maximum allowable size
        std::out_of_range <stdexcept> argument value not in its expected range
    std::runtime_error <stdexcept> errors detectable when the program executes
        std::overflow_error <stdexcept> arithmetic overflow error.
        std::underflow_error <stdexcept> arithmetic underflow error.
        std::range_error <stdexcept> range errors in internal computations
        std::regex_error <regex> errors from the regular expression library.
        std::system_error <system_error> from operating system or other C API
            std::ios_base::failure <ios> Input or output error

 int gcdYisLargerThanX(int x, int y)
{
  return x==0 ? y : gcd(y%x, x);
}

bool isPrime(int n) 
{ 
    // Corner cases 
    if (n <= 1) 
        return false; 
    if (n <= 3) 
        return true; 
  
    // This is checked so that we can skip 
    // middle five numbers in below loop
	// any integer can be expressed as (6k + i), where i = -1, 0, 1, 2, 3, 4
	// (6k + 0), (6k + 2), (6k + 4) covered by n%2
	// (6k + 3) covered by n%3
    if (n % 2 == 0 || n % 3 == 0) 
        return false; 
	
	// Check for 6K + 1 and 6K - 1
    for (int i = 5; i * i <= n; i = i + 6) 
        if (n % i == 0 || n % (i + 2) == 0) 
            return false; 
 
    return true; 
}

int maxSubArray(vector<int>& nums) {
        int maxSum = nums[0], currSum = nums[0];
        
        for(int i=1; i < nums.size(); i++)
        {
            currSum += nums[i];
            if(nums[i] > currSum) currSum = nums[i];
            maxSum = (currSum > maxSum) ? currSum : maxSum;
        }
        return maxSum;
    }