【LeetCode】Tree 合集 - 20230709

树相关主要是dfs和bfs，递归万金油
常用结构 stack 和queue

占位，刷完来写总结

【111】

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
 *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
 * };
 */

// -BFS 
class Solution {
public:
    int minDepth(TreeNode* root) {
        if (root == nullptr) return 0;
        queue que;
        que.push(root);
        int ans = INT_MAX;
        int tree_depth = 1;
        while (!que.empty()) {
            int len = que.size();
            for (int i=0; ileft == nullptr && tmp->right == nullptr) {
                    ans = min(ans, tree_depth);
                    break;
                }
                if (tmp->left) que.push(tmp->left);
                if (tmp->right) que.push(tmp->right);
            }
            tree_depth += 1;
        }
        if (ansleft == nullptr && root->right == nullptr) return 1;
        if (root->right ==  nullptr) {
            return 1+minDepth(root->left);
        }
        if (root->left == nullptr) {
            return 1+ minDepth(root->right);
        }
        // 如果两边都不为空
        return min(1+minDepth(root->left), 1+minDepth(root->right));
    }
};