111. Minimum Depth of Binary Tree - Easy

﹏ヽ暗。殇╰゛Y 2021-09-20 12:52 333阅读 0赞

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],

  1. 3
  2.    / \
  3.   9  20
  4.     /  \
  5.    15   7

return its minimum depth = 2.

time: O(n), space: O(height)

  1. /**
  2.  * Definition for a binary tree node.
  3.  * public class TreeNode {
  4.  *     int val;
  5.  *     TreeNode left;
  6.  *     TreeNode right;
  7.  *     TreeNode(int x) { val = x; }
  8.  * }
  9.  */
  10. class Solution {
  13.     public int minDepth(TreeNode root) {
  14.         if(root == null) {
  15.             return 0;
  16.         }
  17.         if(root.left == null) {
  18.             return minDepth(root.right) + 1;
  19.         }
  20.         if(root.right == null) {
  21.             return minDepth(root.left) + 1;
  22.         }
  23.         return 1 + Math.min(minDepth(root.left), minDepth(root.right));
  24.     }
  25. }

转载于:https://www.cnblogs.com/fatttcat/p/10197070.html

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