Arrays Introduction | HackerRank

Goal

Print the N integers of the array in the reverse order, space-separated on a single line.

Solution

1. Create array with N size.

2. Save N integers into array.

3. Print reverse array with space

// Arrays Introduction

#include <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
using namespace std;


int main() {
    /* Enter your code here. Read input from STDIN. Print output to STDOUT */
    int n;
    
    cin >> n;
    
    int a[n];
    int tmp;
    int i = 0;
    
    while (cin >> tmp)
    {
        a[i] = tmp;
        i++;
    }
    
    for(int index = n - 1; index >=0 ; index--){
        if(index !=0){
            cout << a[index] << " ";
        }
        else{
            cout << a[index] << endl;
        }
    }
    
    
    return 0;
}

Pointer | HackerRank

Goal

By using pointer in C++, save a + b value into a and | a - b | into b.

Solution

This problem makes us to pratice pointer. 

You can save sum and abs_min of a and b with * sign in a and b, respectively. 

// Pointer

#include <stdio.h>
#include <cstdlib>


void update(int *a,int *b) {
    // Complete this function

    int sum = *a + * b;
    
    int abs_min = (*a) - (*b);
    *a = sum;
    *b = abs(abs_min);
        
}

int main() {
    int a, b;
    int *pa = &a, *pb = &b;
    
    scanf("%d %d", &a, &b);
    update(pa, pb);
    printf("%d\n%d", a, b);

    return 0;
}

Functions | HackerRank

Goal

Get four arguments and return the greatest of the four integers

Solution

Because you just need to return the greatest integer.

You can compare a and b first, then c and d.

If you find already greateest integer, you can simply return the value.

// Functions

#include <iostream>
#include <cstdio>
using namespace std;

/*
Add `int max_of_four(int a, int b, int c, int d)` here.
*/

int max_of_four(int a, int b, int c, int d){
    
    
    if(a >= b){
        if (a >= c){
            if (a >= d){
                return a;
            }
            else{
                return d;
            }
        }
            
        else{
            
            if( c>=d){
                return c;
            }
            
            else{
                return d;
            }
        }
    }
    
    else{
        
        if (b >= c){
            if (b >= d){
                return b;
            }
            else {
                return d;
            }
        }
        
        else{
            
            if (c >= d){
                return c;
            }
            
            else {
                return d;
            }
            
        }
        
    }
    
    return 0;
}



int main() {
    int a, b, c, d;
    scanf("%d %d %d %d", &a, &b, &c, &d);
    int ans = max_of_four(a, b, c, d);
    printf("%d", ans);
    
    return 0;
}