111. Minimum Depth of Binary Tree

Description

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.

Constraints

Approach

Examples

Input: [3, 9, 20, null, null, 15, 7]

Output: 2

Solutions

// Definition for a binary tree node.
public class TreeNode {
    int val;
    TreeNode left;
    TreeNode right;
    
    TreeNode() {}
    
    TreeNode(int val) { this.val = val; }
    
    TreeNode(int val, TreeNode left, TreeNode right) {
        this.val = val;
        this.left = left;
        this.right = right;
    }
}

/**
 * Time complexity : 
 * Space complexity : 
 */

class Solution {
    public int minDepth(TreeNode root) {
        if(root == null) return 0;
        
        if(root.left == null) {
            return 1 + minDepth(root.right);
        }
        
        if(root.right == null) {
            return 1 + minDepth(root.left);
        }
        
        return 1 + Math.min(minDepth(root.left), minDepth(root.right));
    }
}

Follow up

Previous110. Balanced Binary Tree Next112. Path Sum

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