Minimum Depth of Binary Tree @LeetCode

/**
 * Minimum Depth of Binary Tree
 * 
 * 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.
 */
public class S111 {

	public static void main(String[] args) {

	}
	
	public int minDepth(TreeNode root) {
		if(root == null){
			return 0;
		}

		int minLeft = minDepth(root.left);
		int minRight = minDepth(root.right);
		
		if(minLeft!=0 && minRight!=0){	// 还没到叶子节点，可以往左右继续走
			return 1 + Math.min(minLeft, minRight);
		}else if(minLeft != 0){		// 还没到叶子节点，可以往左继续走
			return 1 + minLeft;
		}else if(minRight != 0){	// 还没到叶子节点，可以往右继续走
			return 1 + minRight;
		}else{		// 到了叶子节点
			return 1;
		}
    }

}