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111. Minimum Depth of Binary Tree

Posted on Edited on In Disqus:
Symbols count in article: 975 Reading time ≈ 1 mins.

跟104. Maximum Depth of Binary Tree对比
这道题要特别注意一个corner case
[1,2]的mindepth是2不是1
所以不能简单的一行递归

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/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    int minDepth(TreeNode* root) {
        if (!root) return 0;
        int l = minDepth(root->left), r = minDepth(root->right);
        if (!root->left) return r + 1;
        return root->right ? min(l, r) + 1 : l + 1;
    }
};
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/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    int minDepth(TreeNode* root) {
        if (!root) return 0;
        if (!root->left && !root->right) return 1;
        int res = INT_MAX;
        if (root->left) {
            res = min(res, minDepth(root->left));
        }
        if (root->right) {
            res = min(res, minDepth(root->right));
        }
        return res + 1;
    }
};