104. Maximum Depth of Binary Tree

Given a binary tree, find its maximum depth.

The maximum depth is the number of nodes along the longest path from the root node down to the farthest leaf node.

S: Depth first search

    int maxDepth(TreeNode* root) {
        if(!root) return 0;
        return max(maxDepth(root->left), maxDepth(root->right)) + 1;
    }

111. Minimum Depth of Binary Tree

Given a binary tree, find its minimum depth.

The minimum depth is the number of nodes along the shortest path from the root node down to the nearest leaf node.

S: DFS

注意判断是否是leaf node以及root == NULL的特殊处理

    int minDepth(TreeNode* root) {
        if(!root) return 0;
        if(!root->left && !root->right) return 1;
        int left = root->left?minDepth(root->left): INT_MAX;
        int right = root->right?minDepth(root->right): INT_MAX;
        return min(left, right) + 1;
    }