Don't understand what array-1 means

Question

I have a problem with understanding this code, especially the "vet-1" part. What does it mean? What item of the array does it return? Thanks

#include <stdlib>
#include <iostream>

using namespace std;

void change( int m, int n[7]);

int main(){
int vet[] = {1,2,3,4,5};
change(vet[4],vet-1);
change(0,&vet[4]);
int i=0;
for (i=0;i<5;i++) cout << vet[i];
return 0;
}

void change( int m, int n[7]) {
(*(n+m))--; m++; n--;
}

Answer 1

vet - 1 is an attempt at referring to the pointer to the element just before vet[0] .

Actually the behaviour on doing that is undefined . So the entire program is undefined.

Nothing to understand here; move on!