P117、面试题18：树的子结构

题目：输入两棵二叉树A和B，判断B是不是A的子结构。二叉树结点的定义如下：
struct BinaryTreeNode{
       int  m_nValue;
       BinaryTreeNode*    m_pLeft;
       BinaryTreeNode*    m_pRight;
}

代码实现：

package com.yyq;

/**
 * Created by Administrator on 2015/9/15.
 */
public class SubstructureInTree {
    public static boolean hashSubTree(BinaryTreeNode pRoot1, BinaryTreeNode pRoot2) {
        boolean result = false;
        if (pRoot1 != null && pRoot2 != null) {
            if (pRoot1.getM_nValue() == pRoot2.getM_nValue()) {
                result = doesTree1HaveTree2(pRoot1, pRoot2);
            }
            if (!result) {
                result = hashSubTree(pRoot1.getM_pLeft(), pRoot2);
            }
            if (!result) {
                result = hashSubTree(pRoot1.getM_pRight(), pRoot2);
            }
        }
        return result;
    }

    public static boolean doesTree1HaveTree2(BinaryTreeNode pRoot1, BinaryTreeNode pRoot2) {
        if (pRoot2 == null)
            return true;
        if (pRoot1 == null)
            return false;
        if (pRoot1.getM_nValue() != pRoot2.getM_nValue())
            return false;
        return doesTree1HaveTree2(pRoot1.getM_pLeft(), pRoot2.getM_pLeft()) && doesTree1HaveTree2(pRoot1.getM_pRight(), pRoot2.getM_pRight());
    }

    // ====================测试代码====================
    public static void Test(String testName, BinaryTreeNode pRoot1, BinaryTreeNode pRoot2, boolean expected) {
        if (hashSubTree(pRoot1, pRoot2) == expected)
            System.out.println(testName + " passed.");
        else
            System.out.println(testName + " fail.");
    }

    // 树中结点含有分叉，树B是树A的子结构
//                  8                8
//              /                  / 
//             8         7         9   2
//           /   
//          9     2
//               / 
//              4   7
    public static void Test1() {
        BinaryTreeNode pNodeA1 = new BinaryTreeNode(8);
        BinaryTreeNode pNodeA2 = new BinaryTreeNode(8);
        BinaryTreeNode pNodeA3 = new BinaryTreeNode(7);
        BinaryTreeNode pNodeA4 = new BinaryTreeNode(9);
        BinaryTreeNode pNodeA5 = new BinaryTreeNode(2);
        BinaryTreeNode pNodeA6 = new BinaryTreeNode(4);
        BinaryTreeNode pNodeA7 = new BinaryTreeNode(7);

        pNodeA1.connectTreeNodes(pNodeA2, pNodeA3);
        pNodeA2.connectTreeNodes(pNodeA4, pNodeA5);
        pNodeA5.connectTreeNodes(pNodeA6, pNodeA7);

        BinaryTreeNode pNodeB1 = new BinaryTreeNode(8);
        BinaryTreeNode pNodeB2 = new BinaryTreeNode(9);
        BinaryTreeNode pNodeB3 = new BinaryTreeNode(2);

        pNodeB1.connectTreeNodes(pNodeB2, pNodeB3);
        Test("Test1", pNodeA1, pNodeB1, true);
        pNodeA1 = null;
        pNodeB1 = null;
    }

    // 树中结点含有分叉，树B不是树A的子结构
//                  8                8
//              /                  / 
//             8         7         9   2
//           /   
//          9     3
//               / 
//              4   7
    public static void Test2() {
        BinaryTreeNode pNodeA1 = new BinaryTreeNode(8);
        BinaryTreeNode pNodeA2 = new BinaryTreeNode(8);
        BinaryTreeNode pNodeA3 = new BinaryTreeNode(7);
        BinaryTreeNode pNodeA4 = new BinaryTreeNode(9);
        BinaryTreeNode pNodeA5 = new BinaryTreeNode(3);
        BinaryTreeNode pNodeA6 = new BinaryTreeNode(4);
        BinaryTreeNode pNodeA7 = new BinaryTreeNode(7);

        pNodeA1.connectTreeNodes(pNodeA2, pNodeA3);
        pNodeA2.connectTreeNodes(pNodeA4, pNodeA5);
        pNodeA5.connectTreeNodes(pNodeA6, pNodeA7);

        BinaryTreeNode pNodeB1 = new BinaryTreeNode(8);
        BinaryTreeNode pNodeB2 = new BinaryTreeNode(9);
        BinaryTreeNode pNodeB3 = new BinaryTreeNode(2);

        pNodeB1.connectTreeNodes(pNodeB2, pNodeB3);

        Test("Test2", pNodeA1, pNodeB1, false);
        pNodeA1 = null;
        pNodeB1 = null;
    }

    // 树中结点只有左子结点，树B是树A的子结构
//                8                  8
//              /                   /
//             8                   9
//           /                    /
//          9                    2
//         /
//        2
//       /
//      5
    public static void Test3() {
        BinaryTreeNode pNodeA1 = new BinaryTreeNode(8);
        BinaryTreeNode pNodeA2 = new BinaryTreeNode(8);
        BinaryTreeNode pNodeA3 = new BinaryTreeNode(9);
        BinaryTreeNode pNodeA4 = new BinaryTreeNode(2);
        BinaryTreeNode pNodeA5 = new BinaryTreeNode(5);

        pNodeA1.connectTreeNodes(pNodeA2, null);
        pNodeA2.connectTreeNodes(pNodeA3, null);
        pNodeA3.connectTreeNodes(pNodeA4, null);
        pNodeA4.connectTreeNodes(pNodeA5, null);

        BinaryTreeNode pNodeB1 = new BinaryTreeNode(8);
        BinaryTreeNode pNodeB2 = new BinaryTreeNode(9);
        BinaryTreeNode pNodeB3 = new BinaryTreeNode(2);

        pNodeB1.connectTreeNodes(pNodeB2, null);
        pNodeB2.connectTreeNodes(pNodeB3, null);

        Test("Test3", pNodeA1, pNodeB1, true);
        pNodeA1 = null;
        pNodeB1 = null;
    }

    // 树中结点只有左子结点，树B不是树A的子结构
//                8                  8
//              /                   /
//             8                   9
//           /                    /
//          9                    3
//         /
//        2
//       /
//      5
    public static void Test4() {
        BinaryTreeNode pNodeA1 = new BinaryTreeNode(8);
        BinaryTreeNode pNodeA2 = new BinaryTreeNode(8);
        BinaryTreeNode pNodeA3 = new BinaryTreeNode(9);
        BinaryTreeNode pNodeA4 = new BinaryTreeNode(2);
        BinaryTreeNode pNodeA5 = new BinaryTreeNode(5);

        pNodeA1.connectTreeNodes(pNodeA2, null);
        pNodeA2.connectTreeNodes(pNodeA3, null);
        pNodeA3.connectTreeNodes(pNodeA4, null);
        pNodeA4.connectTreeNodes(pNodeA5, null);

        BinaryTreeNode pNodeB1 = new BinaryTreeNode(8);
        BinaryTreeNode pNodeB2 = new BinaryTreeNode(9);
        BinaryTreeNode pNodeB3 = new BinaryTreeNode(3);

        pNodeB1.connectTreeNodes(pNodeB2, null);
        pNodeB2.connectTreeNodes(pNodeB3, null);

        Test("Test4", pNodeA1, pNodeB1, false);
        pNodeA1 = null;
        pNodeB1 = null;
    }

    // 树中结点只有右子结点，树B是树A的子结构
//       8                   8
//                           
//         8                   9
//                             
//           9                   2
//            
//             2
//              
//               5
    public static void Test5() {
        BinaryTreeNode pNodeA1 = new BinaryTreeNode(8);
        BinaryTreeNode pNodeA2 = new BinaryTreeNode(8);
        BinaryTreeNode pNodeA3 = new BinaryTreeNode(9);
        BinaryTreeNode pNodeA4 = new BinaryTreeNode(2);
        BinaryTreeNode pNodeA5 = new BinaryTreeNode(5);

        pNodeA1.connectTreeNodes(null, pNodeA2);
        pNodeA2.connectTreeNodes(null, pNodeA3);
        pNodeA3.connectTreeNodes(null, pNodeA4);
        pNodeA4.connectTreeNodes(null, pNodeA5);

        BinaryTreeNode pNodeB1 = new BinaryTreeNode(8);
        BinaryTreeNode pNodeB2 = new BinaryTreeNode(9);
        BinaryTreeNode pNodeB3 = new BinaryTreeNode(2);

        pNodeB1.connectTreeNodes(null, pNodeB2);
        pNodeB2.connectTreeNodes(null, pNodeB3);

        Test("Test5", pNodeA1, pNodeB1, true);
        pNodeA1 = null;
        pNodeB1 = null;
    }

    // 树A中结点只有右子结点，树B不是树A的子结构
//       8                   8
//                           
//         8                   9
//                           / 
//           9               3   2
//            
//             2
//              
//               5
    public static void Test6() {
        BinaryTreeNode pNodeA1 = new BinaryTreeNode(8);
        BinaryTreeNode pNodeA2 = new BinaryTreeNode(8);
        BinaryTreeNode pNodeA3 = new BinaryTreeNode(9);
        BinaryTreeNode pNodeA4 = new BinaryTreeNode(2);
        BinaryTreeNode pNodeA5 = new BinaryTreeNode(5);

        pNodeA1.connectTreeNodes(null, pNodeA2);
        pNodeA2.connectTreeNodes(null, pNodeA3);
        pNodeA3.connectTreeNodes(null, pNodeA4);
        pNodeA4.connectTreeNodes(null, pNodeA5);

        BinaryTreeNode pNodeB1 = new BinaryTreeNode(8);
        BinaryTreeNode pNodeB2 = new BinaryTreeNode(9);
        BinaryTreeNode pNodeB3 = new BinaryTreeNode(3);
        BinaryTreeNode pNodeB4 = new BinaryTreeNode(2);

        pNodeB1.connectTreeNodes(null, pNodeB2);
        pNodeB2.connectTreeNodes(pNodeB3, pNodeB4);

        Test("Test6", pNodeA1, pNodeB1, false);
        pNodeA1 = null;
        pNodeB1 = null;
    }

    // 树A为空树
    public static void Test7() {
        BinaryTreeNode pNodeB1 = new BinaryTreeNode(8);
        BinaryTreeNode pNodeB2 = new BinaryTreeNode(9);
        BinaryTreeNode pNodeB3 = new BinaryTreeNode(3);
        BinaryTreeNode pNodeB4 = new BinaryTreeNode(2);

        pNodeB1.connectTreeNodes(null, pNodeB2);
        pNodeB2.connectTreeNodes(pNodeB3, pNodeB4);

        Test("Test7", null, pNodeB1, false);
        pNodeB1 = null;
    }

    // 树B为空树
    public static void Test8() {
        BinaryTreeNode pNodeA1 = new BinaryTreeNode(8);
        BinaryTreeNode pNodeA2 = new BinaryTreeNode(9);
        BinaryTreeNode pNodeA3 = new BinaryTreeNode(3);
        BinaryTreeNode pNodeA4 = new BinaryTreeNode(2);

        pNodeA1.connectTreeNodes(null, pNodeA2);
        pNodeA2.connectTreeNodes(pNodeA3, pNodeA4);

        Test("Test8", pNodeA1, null, false);
        pNodeA1 = null;
    }

    // 树A和树B都为空
    public static void Test9() {
        Test("Test9", null, null, false);
    }

    public static void main(String[] args) {
        Test1();
        Test2();
        Test3();
        Test4();
        Test5();
        Test6();
        Test7();
        Test8();
        Test9();
    }
}

 

输出结果：

Test1 passed.

Test2 passed.

Test3 passed.

Test4 passed.

Test5 passed.

Test6 passed.

Test7 passed.

Test8 passed.

Test9 passed.