How do you write a recursive procedure that returns the smallest value in an array of 10 elements?

Answer 1

The operation you describe is not a recursive one, it is iterative (linear in nature). It's also better to return the index of the smallest value rather than just the value itself. In this way we know the position of the smallest value as well as the value itself.

To find the smallest element in an array, we start with the first element. Being the only value encountered so far, it must be the smallest, so we store its index. We then compare the value at the stored index to that of each of the remaining elements, one by one. When we find a smaller value, we update the stored index, because that value is the smallest encountered so far. When we reach the end of the array, the stored index will tell us which element was the smallest, so we simply return that index.

The algorithm can (and should) be generalised to cater for arrays of any length.

// Returns the index of the smallest value in array a of length n

int smallest (const int* const a, int n) {

if (n<1) return -1; // sanity check: the array must have 1 or more elements to be valid

int i, j;

i = 0; // assume first element holds smallest value until proven otherwise

for (j=1; j<n; ++j) if (a[j] < a[i]) i = j; // update i each time a smaller value is found at index j

return i; // a[i] holds the smallest value in the array

}

int main (void) {

const int max = 10; int a[max] = {5, 4, 6, 3, 0, 7, 2, 8, 1, 9};

int i;

i = smallest (a, max);

assert (i==4); // a[4] holds the smallest value

return 0;

}