c++ sorting 5 numbers using only if-statements

sort_5_numbers.cpp

#include<iostream>

void swap(int& a, int& b){
    // Swap 2 numbers using a temporary variable.
    int temp;
    temp = a;
    a = b;
    b = temp;
}
int* sort(int a[]){
    // Part a
    if(a[1] < a[0])
        swap(a[1],a[0]);
    if(a[2] < a[1]){
        swap(a[2],a[1]);
        if(a[1] < a[0])
            swap(a[1],a[0]);
    }
    // Part b
    if(a[3] < a[2]){
        swap(a[3], a[2]);
        if(a[1] < a[0])
            swap(a[1],a[0]);
        if(a[2] < a[1]){
            swap(a[2],a[1]);
            if(a[1] < a[0])
                swap(a[1],a[0]);
        }
    }
    // Part c
    if(a[4] < a[3]){
        swap(a[4],a[3]);
            if(a[3] < a[2]){
                swap(a[3], a[2]);
                if(a[1] < a[0])
                    swap(a[1],a[0]);
                if(a[2] < a[1]){
                    swap(a[2],a[1]);
                    if(a[1] < a[0])
                        swap(a[1],a[0]);
            }
    }

    }
    return a;
        
    
}
// Testing the algorithm
int main()
{
    int a[] = {4,5,7,9,6};
    int* b = sort(a);
    for(int i=0; i<5; i++)
        std::cout<<b[i]<<" ";
    std::cout<<std::endl;
}