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.

 

思想：递归即可

注意事项： 如果left或者right为空，需要忽略；

1. public int minDepth(TreeNode root) {
2. if(root == null) return 0;
3. if(root.left == null && root.right == null) return 1;
4. if(root.left == null) return minDepth(root.right)+1;
5. if(root.right == null) return minDepth(root.left)+1;
6. return Math.min(minDepth(root.left),minDepth(root.right))+1;
7. }

C++代码：

1. int minDepth(TreeNode *root) {
2. if(root==NULL) return 0;
3. int leftmin = minDepth(root->left);
4. int rightmin = minDepth(root->right);
5. if(leftmin * rightmin != 0) return min(leftmin,rightmin)+1;
6. else if(rightmin==0) return leftmin+1;
7. else if(leftmin==0) return rightmin+1; // notice whether the left tree is null or the right tree is null
8. }