Given a pre order, find whether it is single child BST

#include <stdio.h>
#include <limits.h>

int isSingleChildBST(int a[], int n){

        int mx = INT_MAX, i;

        for(i = 1; i < n ; ++i){

                if(a[i] <= a[i - 1]){    //assuming equal elements are in left tree
                        mx = a[i - 1];
                }else{
                        if(a[i] > mx)
                                return 0;
                }
        }

        return 1;

}

int main(){

        int a[] = {10,19,17,14,15,16};

        printf("%s\n", isSingleChildBST(a, 6) ? "YES" : "NO");
        return 0;
}