力扣算法题—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.
Note: A leaf is a node with no children.
Example:
Given binary tree [3,9,20,null,null,15,7],
3
/ \
9 20
/ \
15 7
return its minimum depth = 2.
Solution:
使用深度遍历和广度遍历
1 class Solution { 2 private: 3 int minLevel = INT32_MAX; 4 public: 5 int minDepth(TreeNode* root) { 6 if (root == nullptr)return 0; 7 //return BFS(root); 8 int res = INT32_MAX; 9 DFS(root, 1, res); 10 return res; 11 } 12 13 int BFS(TreeNode* root) 14 { 15 queue<TreeNode*>q; 16 q.push(root); 17 int level = 0; 18 while (!q.empty()) 19 { 20 queue<TreeNode*>temp; 21 ++level; 22 while (!q.empty()) 23 { 24 TreeNode* p = q.front(); 25 q.pop(); 26 if (p->left == nullptr && p->right == nullptr)return level; 27 if (p->left != nullptr)temp.push(p->left); 28 if (p->right != nullptr)temp.push(p->right); 29 } 30 q = temp; 31 } 32 return level; 33 } 34 void DFS(TreeNode* root, int level, int &res) 35 { 36 if (root->left == nullptr && root->right == nullptr) { 37 res = res > level ? level : res; 38 return; 39 } 40 if (root->left != nullptr)DFS(root->left, level + 1, res); 41 if (root->right != nullptr)DFS(root->right, level + 1, res); 42 } 43 44 };
