LeetCode - 257 Binary Tree Paths

最新推荐文章于 2024-11-03 20:00:49 发布

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class Solution {
public:
    string make_path(stack<TreeNode *> st){
        string s,temp;
        TreeNode *pre=st.top()->left;
        while(!st.empty()){
            TreeNode *cur=st.top();
            if(cur->left!=pre&&cur->right!=pre){
                st.pop();
                continue;
            }
            stringstream ss;
            ss<<cur->val;
            temp=ss.str();
            if(s==""){
                s=temp;
            }
            else{
                s=temp+"->"+s;
            }
            pre=cur;
        }
        return s;
    }
    vector<string> binaryTreePaths(TreeNode* root) {
        vector<string> res;
        string str;
        if(root==NULL){
            return res;
        }
        stack<TreeNode *> st;
        st.push(root);
        TreeNode *pre=root;
        while(!st.empty()){
            TreeNode *cur=st.top();
            if(pre!=cur->left&&pre!=cur->right){
                if(cur->right!=NULL){
                    st.push(cur->right);
                }
                if(cur->left!=NULL){
                    st.push(cur->left);
                }
                if(cur->left==NULL&&cur->right==NULL){
                    res.push_back(make_path(st));
                    pre=cur;
                    st.pop();
                }
            }
            else{
                pre=cur;
                st.pop();
            }
        }
    }
};