解法：

#include<iostream>
#include<queue>
using namespace std;
// 定义二叉树结点
struct TreeNode {
    char val;
    TreeNode* left;
    TreeNode* right;
    TreeNode(char x) :val(x), left(NULL), right(NULL) {};
};
// 先序递归遍历建立二叉树
TreeNode* buildTree() {
    char c;
    cin >> c;
    if (c == '#') {
        return NULL;
    }
    TreeNode* root = new TreeNode(c);
    root->left = buildTree();
    root->right = buildTree();
    return root;
}
int dfs(TreeNode* root) {
    if (root == NULL) return 0;
    if (root->left==NULL&&root->right==NULL) return 1;

    int left = dfs(root->left);
    int right = dfs(root->right);

    return left + right;
}
int main() {
    TreeNode* root= buildTree();
    cout<<dfs(root);
    return 0;
}