minimum-depth-of-binary-tree

 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 TreeNode {
	    int val;
	    TreeNode left;
	    TreeNode right;
	    TreeNode(int x) { val = x; }
	}

	public int run(TreeNode root) {
	
            if(root == null)
                return 0;
            int i = run(root.left);
            int j = run(root.right);
        
            //左右子树有一个为空就是另外一边的深度加 1 为该节点的最小深度
            return (i == 0 || j == 0) ? i + j + 1 : Math.min(i, j) + 1;
		
        }
	
	@Test
	public void test() {
		TreeNode root = new TreeNode(1);
		
		TreeNode temp = root;
		temp.left = new TreeNode(2);
		temp.right = new TreeNode(3);
		
		TreeNode temp1 = temp.left;
		temp1.left = new TreeNode(4);
		temp1.right = new TreeNode(5);
		
		TreeNode temp2 = temp.right;
		temp2.left = new TreeNode(6);
		//temp2.right = new TreeNode(7);
		
		System.out.println(run(root));
	}