树的层次遍历

题目

LeetCode102.二叉树的层序遍历

代码

class Solution {
public:
    
    vector<vector<int>>ans;
    vector<vector<int>> levelOrder(TreeNode* root) {
        if(root == NULL ) return ans;
        queue<TreeNode*>q;
        q.push(root);
        while(!q.empty()){
            int sum = q.size();
            vector<int>path;
            for(int i = 0;i < sum;i++){ //控制当前层全部弹出
                auto t = q.front();path.push_back(t->val);
                q.pop();
                if(t->left!=NULL) {q.push(t->left);}
                if(t->right!=NULL) {q.push(t->right);}
            }
            ans.push_back(path); 
        } 
        return ans;
    }
};

题目

LeetCode199. 二叉树的右视图

代码

class Solution {
public:
    vector<int>ans;
    vector<int> rightSideView(TreeNode* root) {
        if(root==NULL) return ans;
        queue<TreeNode*>q;
        q.push(root);
        while(!q.empty()){
            int sum = q.size();
            TreeNode* t;
            for(int i = 0;i < sum;i++){
                t = q.front();q.pop();
                if(t->left!=NULL) q.push(t->left);
                if(t->right!=NULL) q.push(t->right);
            }
            ans.push_back(t->val);
        }
        return ans;
    }
};

题目

LeetCode429. N 叉树的层序遍历

代码

class Solution {
public:
    vector<vector<int>>ans;
    vector<vector<int>> levelOrder(Node* root) {
        if(root == NULL) return ans;
        queue<Node*>q;
        q.push(root);
        while(!q.empty()){
            int sum = q.size();
            vector<int>path;
            for(int i = 0;i < sum;i++){
                auto t = q.front();q.pop();path.push_back(t->val);
                for(int i = 0;i < t->children.size();i++){
                    if(t->children[i] != NULL) q.push(t->children[i]);
                }
            }
            ans.push_back(path);
        }
        return ans;
    }
};