LeetCode 111. Minimum Depth of Binary Tree

Problem:

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.

Solution:

DFS

/**
 * Definition for a binary tree node.
 * 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 minDepth(root, 0);
    }
    
    private int minDepth(TreeNode root, int current) {
        if (root.left == null && root.right == null) return current + 1;
        else if (root.left == null) return minDepth(root.right, current + 1);
        else if (root.right == null) return minDepth(root.left, current + 1);
        else return Math.min(minDepth(root.left, current + 1), minDepth(root.right, current + 1));
    }
}

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