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    1. public class TreeDeep {
    2.     public static void main(String[] args) {
    3.         TreeNode treeNode7 = new TreeNode(7,null, null);
    4.         TreeNode treeNode6 = new TreeNode(6, treeNode7, null);
    5.         TreeNode treeNode5 = new TreeNode(5,null, treeNode6);
    6.         TreeNode treeNode4 = new TreeNode(4,null, null);
    7.         TreeNode treeNode3 = new TreeNode(3,null, null);
    8.         TreeNode treeNode2 = new TreeNode(2, treeNode3, treeNode4);
    9.         TreeNode treeNode1 = new TreeNode(1, treeNode2, treeNode5);
    10.         System.out.println(minDepth(treeNode1));
    12.      }
    14.     private static int minDepth(TreeNode treeNode) {
    15.         if (null == treeNode) return 0;
    17.         // 遍历到叶子节点
    18.         if (null == treeNode.left && null == treeNode.right) return 1;
    20.         int depth = Integer.MAX_VALUE;
    21.         if (null != treeNode.left) {
    22.             // 递归遍历左节点的深度
    23.             depth = Math.min(minDepth(treeNode.left), depth);
    24.         }
    26.         if (null != treeNode.right) {
    27.             // 递归遍历右节点的深度
    28.             depth = Math.min(minDepth(treeNode.right), depth);
    29.         }
    31.         return depth + 1;
    32.     }
    34.     static class TreeNode{
    35.         int val;
    36.         private TreeNode left;
    37.         private TreeNode right;
    38.         int deep;
    40.         public TreeNode(int val, TreeNode left, TreeNode right) {
    41.             this.val = val;
    42.             this.left = left;
    43.             this.right = right;
    44.         }
    45.     }
    46. }