This is a solution I came up with while trying to find a unique, extensible way to find the greatest value in a collection of integers. The real cool stuff here exists in the function get_greatest. I could have used a sorting algorithm and then returned the greatest value, but finding a recursive solution was a lot of fun. Very roughly speaking,…

Recursive Find Max Val of Any N Ints

/*
    This is a solution I came up with while trying to find a unique, extensible way to find the greatest value in a collection of integers.
    The real cool stuff here exists in the function get_greatest.
    I could have used a sorting algorithm and then returned the greatest value, but finding a recursive solution was a lot of fun.
    Very roughly speaking, the time complexity estimate is between O(n) and O(n^2).
    Really the function runs as follows (each term is a new recursive scope): n + (n - 1) + (n - 2) + ... + (n - (n - 2)).
    For example if n is 5: 5 + 4 + 3 + 2 = 14.
*/

#include <iostream>
using namespace std;

int max_of_four(int a, int b, int c, int d);
int get_greatest(int arr[], int sizeOf);

int main() {
    int a, b, c, d;
    cin >> a >> b >> c >> d;
    int ans = max_of_four(a, b, c, d);
    cout << ans;
    
    return 0;
}

int max_of_four(int a, int b, int c, int d)
{
    int arr[4] = { a, b, c, d };
    return get_greatest(arr, 4);
}

int get_greatest(int arr[], int sizeOf)
{
    // Base case
    if (sizeOf == 1)
        return arr[0];

    // Recursive case
    int* nxtArr = new int[sizeOf - 1];
    int dntFillIndx;
    if (arr[0] > arr[1])
        dntFillIndx = 1;
    else
        dntFillIndx = 0;
    int j = 0;
    for (int i = 0; i < sizeOf; i++)
    {
        if (i == dntFillIndx)
            continue;
        nxtArr[j] = arr[i];
        j++;
    }
    int greatest = get_greatest(nxtArr, sizeOf - 1);
    delete [] nxtArr;
    return greatest;
}