[LeetCode]Minimum Depth of Binary Tree

最新推荐文章于 2023-12-15 03:22:29 发布

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最新推荐文章于 2023-12-15 03:22:29 发布

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分类专栏： LeetCode

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本文介绍了一种求解二叉树最小深度的有效算法。通过递归和广度优先搜索两种方法实现，针对不同情况进行了优化处理。适用于面试备考及算法优化实践。

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struct TreeNode {
	int val;
	TreeNode *left;
	TreeNode *right;
	TreeNode(int x) : val(x), left(NULL), right(NULL) {}
};

class Solution {
	//find the minimum step of a tree, bfs works at most time
public:
	int BFS(TreeNode* root)
	{
		if(!root) 
			return 0;
        queue<pair<TreeNode*, int>> q;
		q.push(make_pair(root, 1));
		while(!q.empty())
		{
			TreeNode* curNode = q.front().first;
			int curStep = q.front().second;
			q.pop();//note here
			if(!curNode->left && !curNode->right)
				return curStep;
			if(curNode->left)
				q.push(make_pair(curNode->left, curStep+1));
			if(curNode->right)
				q.push(make_pair(curNode->right, curStep+1));
		}
	}
    int minDepth(TreeNode *root) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
		return BFS(root);
    }
};

second time

/**
 * Definition for binary tree
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    int minDepth(TreeNode *root) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        if(root == NULL) return 0;
        
        if(root->left == NULL) return minDepth(root->right)+1;
        else if(root->right == NULL) return minDepth(root->left)+1;
        else return min(minDepth(root->left), minDepth(root->right))+1;
    }
};