Binary Trees Practice problems

/*Write a menu-driven program to display the number of nodes, height of the tree, maximum and minimum values, leaf and non-leaf nodes, sum of all nodes of the tree and odd & even values.*/

#include <stdio.h>
#include <stdlib.h>
struct tree{
    int data;
    struct tree *left,*right;
}*root = NULL;
int totalCount, evenCount, oddCount;
void insert(int value){
    struct tree *newNode = (struct tree*) malloc(sizeof(struct tree));
    newNode->data = value; newNode->right = newNode->left = NULL;
    if(!root)   root = newNode;
    else{
        struct tree *help = root, *previous = NULL;
        while(help){
            previous = help;
            if(value > help->data) help = help ->right;
            else help = help->left;
        }
        if(value > previous->data)   previous->right = newNode;
        else previous->left = newNode;
    }
}
void count(struct tree* help){
    if(help){
        count(help->right);
        totalCount++;
        count(help->left);
    }
}
int height(struct tree *help){
    int leftHeight, rightHeight;
    if(!help)   return 0;
    leftHeight = height(help->left);
    rightHeight = height(help->right);
    if(leftHeight > rightHeight)    return leftHeight+1;
    else return rightHeight+1;
}
int largest(struct tree* help){
    if(!help)   return 0;
    else if (!help-> right) return help->data;
    else return largest(help->right);
}
int smallest(struct tree* help){
    if(!help)   return 0;
    else if (!help-> left) return help->data;
    else return smallest(help->left);
}
int leaf(struct tree *help){
    if(help){
        if(!help->right && !help->left){
            printf("%d ", help-> data);
            return 1;
        }
        else return leaf(help->left) + leaf(help->right);
    }
    else return 0;
}
int nonleaf(struct tree *help){
    if(help){
        if(help->right || help->left){
            printf("%d ", help-> data);
            return 1 + nonleaf(help->left) + nonleaf(help->right);
        }
    }
    else return 0;
}
int sum(struct tree* help){
    if(help)
        return help->data + sum(help->right) + sum(help->left);
    else return 0;
}
void odd(struct tree *help){
    if(help){
        odd(help->right);
        if(help->data % 2 == 1 || help->data % 2 == -1){
            oddCount++;
            printf("%d ", help->data);
        }
        odd(help->left);
    }
}
void even(struct tree *help){
    if(help){
        even(help->right);
        if(help->data % 2 == 0){
            evenCount++;
            printf("%d ", help->data);
        }
        even(help->left);
    }
}
int main(){
    int n;
    up: printf("\nEnter nodes, input -1 to stop.\n");
    while(1){
        printf("\nInput: ");
        scanf("%d",&n);
        if(n==-1) break;
        insert(n);
    }
    printf("\n1.Total 2.Height 3.Max 4.Min 5.Leaf 6.Non-Leaf 7.Sum 8.Odd 9.Even 10.Exit 11.Insert\n");
    while(1){
        printf("\n\nSelect an option: ");
        scanf("%d",&n);
        switch(n){
            case 1: totalCount = 0; count(root); printf("\nThe number of nodes: %d.", totalCount);break;
            case 2: printf("\nThe height of the tree is %d.", height(root)-1); break;
            case 3: printf("The maximum value is %d.", largest(root)); break;
            case 4: printf("The minimum value is %d.", smallest(root)); break;
            case 5: printf("\n%d leaf node(s) found:  ", leaf(root)); break;
            case 6: printf("\n%d non-leaf node(s) found.", nonleaf(root)); break;
            case 7: printf("\n The sum of all the elements in the tree is %d.",sum(root));   break;
            case 8: odd(root); printf("\n%d odd node(s) found.", oddCount); break;//
            case 9: even(root); printf("\n%d even node(s) found.", evenCount); break;
            case 10:return 0;
            case 11: goto up;
            default: printf("\nEnter a number in between 1 and 12.");
        }
    }
}