Minimum Depth of Binary Tree - Javascript

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.

Tags
BFS, DFS, Tree
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/**
* Definition for a binary tree node.
* function TreeNode(val) {
* this.val = val;
* this.left = this.right = null;
* }
*/
/**
* @param {TreeNode} root
* @return {number}
*/
var minDepth = function(root) {
if(root === null) {
return 0;
} else if(root.left === null && root.right === null) {
return 1;
} else if(root.left === null) {
return minDepth(root.right) + 1;
} else if(root.right === null) {
return minDepth(root.left) + 1;
} else {
return Math.min(minDepth(root.left), minDepth(root.right)) + 1;
}
};