LeetCode My Solution: Minimum Depth of Binary Tree

Minimum Depth of Binary Tree

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Submissions: 83665My Submissions

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.

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/**
* Definition for binary tree
* public class TreeNode {
*     int val;
*     TreeNode left;
*     TreeNode right;
*     TreeNode(int x) { val = x; }
* }
*/
public class Solution {
public int minDepth(TreeNode root) {
if (root == null){
return 0;
}
return helper(root);
}
//这个题目和求最大(最小深度)不一样的是要走到叶子节点才算行,也就说要到了叶子节点才OK
//最开始的时候采取了(root == null)的判断，报错，是因为对根节点的处理中认为是求最大的深度，而最小的深度实际是到了
//叶子节点之后才算行
int helper(TreeNode root) {
if (root.left == null && root.right == null) {
return 1;
}
if (root.left == null) {
return helper(root.right) + 1;
}
if (root.right == null) {
return helper(root.left) + 1;
}
else {
return Math.min(helper(root.left),helper(root.right)) + 1;
}
}
}