LeetCode66|二叉树的最小深度

示例:

给定二叉树 [3,9,20,null,null,15,7],

    3
   / \
  9  20
    /  \
   15   7
返回它的最小深度  2.

 

public class MinDepthTest {
    public static void main(String[] args) {
        TreeNode t1 = new TreeNode(3);
        TreeNode t2 = new TreeNode(9);
        TreeNode t3 = new TreeNode(20);
        TreeNode t4 = new TreeNode(15);
        TreeNode t5 = new TreeNode(7);
        t1.left = t2;
        t1.right = t3;
        t3.left = t4.left;
        t3.right = t5;
        int depth = minDepth(t1);
        System.out.println("depth = " + depth);

    }

    public static int minDepth(TreeNode root) {
        if (root == null) {
            return 0;
        }
        if (root.left == null && root.right == null) {
            return 1;
        }
        Integer minValue = Integer.MAX_VALUE;
        if (root.left != null) {
            minValue = Math.min(minDepth(root.left), minValue);
        }
        if (root.right != null) {
            minValue = Math.min(minDepth(root.right), minValue);
        }
        return minValue + 1;
    }
}