統計所有結點數：

//統計所有結點數
int n1=0;
void countAllNode(BTNode *p)
{
    if(p!=NULL)
    {
        ++n1;
        countAllNode(p->lchild);
        countAllNode(p->rchild);
    }
}

統計葉子結點數：

//統計葉子結點數
int n2=0;
void countLeafNode(BTNode *p)
{
    if(p!=NULL)
    {
        if(p->lchild==NULL&&p->rchild==NULL)//判斷是否葉子結點
            ++n2;
        countLeafNode(p->lchild);
        countLeafNode(p->rchild);
    }
}
 

完整測試程式碼：

#include <bits/stdc++.h>
#define MaxSize 100
/*
 * Created by HarvestWu on 2018/06/22.
 */
using namespace std;

typedef char ElemType;

//定義二叉樹結構
typedef struct BTNode
{
    ElemType data;
    struct BTNode *lchild;
    struct BTNode *rchild;
} BTNode;

//由先序遍歷、中序遍歷結果構建二叉樹
BTNode *CreateBT(ElemType pre[],ElemType in[],int l1,int r1,int l2,int r2)
{
    BTNode *s;
    int i;
    if(l1>r1)return NULL;       //序列中無元素返回NULL
    s=(BTNode*)malloc(sizeof(BTNode));
    s->lchild=s->rchild=NULL;
    for(i=l2; i<=r2; ++i)
        if(in[i]==pre[l1])      //查詢等於當前子樹根的結點在in[]中的位置
            break;
    s->data=in[i];
    s->lchild=CreateBT(pre,in,l1+1,l1+i-l2,l2,i-1);
    s->rchild=CreateBT(pre,in,l1+i-l2+1,r1,i+1,r2);
    return s;       //當前子樹處理完畢
}

//統計所有結點數
int n1=0;
void countAllNode(BTNode *p)
{
    if(p!=NULL)
    {
        ++n1;
        countAllNode(p->lchild);
        countAllNode(p->rchild);
    }
}

//統計葉子結點數
int n2=0;
void countLeafNode(BTNode *p)
{
    if(p!=NULL)
    {
        if(p->lchild==NULL&&p->rchild==NULL)
            ++n2;
        countLeafNode(p->lchild);
        countLeafNode(p->rchild);
    }
}


int main()
{
    BTNode *p;
    ElemType pre[]= {'A','B','D','E','H','J','K','L','M','N','C','F','G','I'};
    ElemType in[]={'D','B','J','H','L','K','M','N','E','A','F','C','G','I'};
    
    //由先序遍歷、中序遍歷結果構建二叉樹
    p=CreateBT(pre,in,0,13,0,13);

    cout<<"統計所有結點數:"<<endl;
    countAllNode(p);
    cout<<n1<<endl;


    cout<<"統計葉子結點數:"<<endl;
    countLeafNode(p);
    cout<<n2<<endl;
    return 0;
}