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22 lines
955 B
Markdown
22 lines
955 B
Markdown
# [111. Minimum Depth of Binary Tree](https://leetcode.com/problems/minimum-depth-of-binary-tree/description/)
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# 思路
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求二叉树的最小深度。依次分为以下情况:
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* 若为空树，则返回0；
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* 否则，若左右子树都为空，返回1；
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* 否则，若左子树为空，那么最小深度就为右子树的最小深度加1；若右子树为空，那么最小深度就为左子树的最小深度加1；
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* 否则(即左右子树都不空)，那么最小深度就是min(1+左子树最小深度, 1+右子树最小深度)；
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# C++
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``` C++
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class Solution {
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public:
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int minDepth(TreeNode* root) {
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if(root == NULL) return 0;
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else if(root -> left == NULL && root -> right == NULL) return 1;
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else if(root -> left == NULL) return 1 + minDepth(root -> right);
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else if(root -> right == NULL) return 1 + minDepth(root -> left);
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return 1 + min(minDepth(root -> left), minDepth(root -> right));
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}
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};
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```
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