LeetCode-111.Mininum 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.

 public int minDepth(TreeNode root) {//树 递归 mytip
         if(null==root){
             return 0;
         }
         int left = minDepth(root.left);
         int right = minDepth(root.right);
         int d=left>right?(right+1):(left+1);
         if(left==0||right==0){//注意 单孩子的判断
             d= left+right+1;
         }
         return d;
     }

还可以使用BFS的方法

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