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前言

Github：https://github.com/HealerJean

博客：http://blog.healerjean.com

1、相同的数

给定两个二叉树，编写一个函数来检验它们是否相同。

如果两个树在结构上相同，并且节点具有相同的值，则认为它们是相同的。

示例 1:

 输入:       1         1
          / \       / \
         2   3     2   3
         
 输出: true

示例 2:

输入:      1          1
          /           \
         2             2   
输出: false

示例 3:

输入:       1         1
          / \       / \
         2   1     1   2
         
输出: false

1.1、解题思路

深度优先搜索

1.2、算法

public boolean isSameTree(TreeNode p, TreeNode q) {
    if ((p == null && q == null)) {
        return true;
    } else if (p == null && q != null) {
        return false;
    } else if (q == null && p != null) {
        return false;
    } else if (p.val != q.val) {
        return false;
    }
    //到了这里说明 p.val == q.val
    return isSameTree(p.left, q.left) && isSameTree(p.right, q.right);
}

1.3、测试

@Test
    public void test() {
        System.out.println(isSameTree(null, initTreeNode2()));
    }


    public TreeNode initTreeNode() {
        TreeNode treeNode1 = new TreeNode(3, null, null);
        TreeNode treeNode2 = new TreeNode(6, null, null);
        TreeNode treeNode3 = new TreeNode(4, treeNode1, treeNode2);
        TreeNode treeNode4 = new TreeNode(1, null, null);
        TreeNode root = new TreeNode(5, treeNode3, treeNode4);
        return root;
    }


    public TreeNode initTreeNode2() {
        TreeNode treeNode1 = new TreeNode(3, null, null);
        TreeNode treeNode2 = new TreeNode(6, null, null);
        TreeNode treeNode3 = new TreeNode(4, treeNode1, treeNode2);
        TreeNode treeNode4 = new TreeNode(1, null, null);
        TreeNode root = new TreeNode(5, treeNode3, treeNode4);
        return root;
    }

    public class TreeNode {
        int val;
        TreeNode left;
        TreeNode right;

        TreeNode(int x) {
            val = x;
        }

        TreeNode(int x, TreeNode left, TreeNode right) {
            this.val = x;
            this.left = left;
            this.right = right;

        }
    }

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