LeetCode 257打印所有二叉樹根到葉子的路徑

LeetCode 257
棧的方式實現以及遞歸實現(註釋掉了)，還可以通過隊列方式實現，最終的輸出順序和棧實現的不一樣。

#include <iostream>
#include <string>
#include <sstream>
#include <queue>
#include <stack>
using namespace std;


struct TreeNode {
    int val;
    TreeNode *left;
    TreeNode *right;
    TreeNode(int x) : val(x), left(NULL), right(NULL) {}
};

class Solution {
public:
    string int2string(int val)
    {
        stringstream stream;
        string result;
        stream << val;
        stream >> result;
        stream.clear();
        return result;
    }
#if 0
    void recurseve(vector<string> &res, TreeNode *root, string str)
    {
        if (root == NULL)
            return;
        str = str + int2quring(root->val) ;
        if (root->left == NULL && root->right == NULL)
        {
            cout << str<<endl;
            res.push_back(str);
            return;
        }
        str = str  +  "->";
        if (root->left)
        {
            recurseve(res,root->left,str);
        }
        if (root->right)
        {
            recurseve(res,root->right,str);
        }
    }

    vector<string> binaryTreePaths(TreeNode* root) {
        vector<string> res;
        string  str= "";
        recurseve(res, root, str);
        return res;
    }
#endif // 0
    vector<string> binaryTreePaths(TreeNode* root) {
        stack<TreeNode*> st_node;
        stack<string> st_str;
        vector<string> res;
        TreeNode *tmp;
        string tmp_str;
        if (root == NULL)
            return res;
        st_node.push(root);
        st_str.push(int2string(root->val));
        while(!st_node.empty() && !st_str.empty())
        {
            tmp = st_node.top();
            tmp_str = st_str.top();
            st_node.pop();
            st_str.pop();
            if (tmp->left == NULL && tmp->right == NULL)
            {
                cout <<tmp_str<<endl;
                res.push_back(tmp_str);
            }
            if (tmp->left != NULL)
            {
                st_node.push(tmp->left);
                st_str.push(tmp_str + "->" + int2string(tmp->left->val));
            }
            if (tmp->right != NULL)
            {
                st_node.push(tmp->right);
                st_str.push(tmp_str + "->" + int2string(tmp->right->val));
            }

        }
        return res;
    }
};

int main()
{
    TreeNode *a = new TreeNode(1);
    TreeNode *b = new TreeNode(2);
    TreeNode *c = new TreeNode(3);
    TreeNode *d = new TreeNode(5);

    a->left = b;
    a->right = c;
    b->left = NULL;
    b->right = d;

    Solution s;
    s.binaryTreePaths(a);
    return 0;
}