把二叉树打印成多行

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问题:从上到下按层打印二叉树，同一层的结点按从左到右的顺序打印到一行。例如:

打印结果:

6 10

5 7 9 11

分析：为了把二叉树的每一行单独打印到一行里，我们需要两个变量：一个变量表示在当前层中还没有打印的结点数，另一个变量表示下一层结点的数目。

//按照行打印二叉树void Print(BinaryTreeNode* pRoot){    if(pRoot == NULL)        return;    std::queue<BinaryTreeNode*> nodes;    nodes.push(pRoot);    int nextLevel = 0;    int toBePrinted = 1;    while(!nodes.empty())    {        BinaryTreeNode* pNode = nodes.front();        printf("%d ", pNode->m_nValue);        if(pNode->m_pLeft != NULL)        {            nodes.push(pNode->m_pLeft);            ++nextLevel;        }        if(pNode->m_pRight != NULL)        {            nodes.push(pNode->m_pRight);            ++nextLevel;        }        nodes.pop();        --toBePrinted;        if(toBePrinted == 0)        {            printf("\n");            toBePrinted = nextLevel;            nextLevel = 0;        }    }}// ==================== Test Code ====================//            8//        6      10//       5 7    9  11void Test1(){    BinaryTreeNode* pNode8 = CreateBinaryTreeNode(8);    BinaryTreeNode* pNode6 = CreateBinaryTreeNode(6);    BinaryTreeNode* pNode10 = CreateBinaryTreeNode(10);    BinaryTreeNode* pNode5 = CreateBinaryTreeNode(5);    BinaryTreeNode* pNode7 = CreateBinaryTreeNode(7);    BinaryTreeNode* pNode9 = CreateBinaryTreeNode(9);    BinaryTreeNode* pNode11 = CreateBinaryTreeNode(11);    ConnectTreeNodes(pNode8, pNode6, pNode10);    ConnectTreeNodes(pNode6, pNode5, pNode7);    ConnectTreeNodes(pNode10, pNode9, pNode11);    printf("====Test1 Begins: ====\n");    printf("Expected Result is:\n");    printf("8 \n");    printf("6 10 \n");    printf("5 7 9 11 \n\n");    printf("Actual Result is: \n");    Print(pNode8);    printf("\n");    DestroyTree(pNode8);}//            5//          4//        3//      2void Test2(){    BinaryTreeNode* pNode5 = CreateBinaryTreeNode(5);    BinaryTreeNode* pNode4 = CreateBinaryTreeNode(4);    BinaryTreeNode* pNode3 = CreateBinaryTreeNode(3);    BinaryTreeNode* pNode2 = CreateBinaryTreeNode(2);    ConnectTreeNodes(pNode5, pNode4, NULL);    ConnectTreeNodes(pNode4, pNode3, NULL);    ConnectTreeNodes(pNode3, pNode2, NULL);    printf("====Test2 Begins: ====\n");    printf("Expected Result is:\n");    printf("5 \n");    printf("4 \n");    printf("3 \n");    printf("2 \n\n");    printf("Actual Result is: \n");    Print(pNode5);    printf("\n");    DestroyTree(pNode5);}//        5//         4//          3//           2void Test3(){    BinaryTreeNode* pNode5 = CreateBinaryTreeNode(5);    BinaryTreeNode* pNode4 = CreateBinaryTreeNode(4);    BinaryTreeNode* pNode3 = CreateBinaryTreeNode(3);    BinaryTreeNode* pNode2 = CreateBinaryTreeNode(2);    ConnectTreeNodes(pNode5, NULL, pNode4);    ConnectTreeNodes(pNode4, NULL, pNode3);    ConnectTreeNodes(pNode3, NULL, pNode2);    printf("====Test3 Begins: ====\n");    printf("Expected Result is:\n");    printf("5 \n");    printf("4 \n");    printf("3 \n");    printf("2 \n\n");    printf("Actual Result is: \n");    Print(pNode5);    printf("\n");    DestroyTree(pNode5);}void Test4(){    BinaryTreeNode* pNode5 = CreateBinaryTreeNode(5);    printf("====Test4 Begins: ====\n");    printf("Expected Result is:\n");    printf("5 \n\n");    printf("Actual Result is: \n");    Print(pNode5);    printf("\n");    DestroyTree(pNode5);}void Test5(){    printf("====Test5 Begins: ====\n");    printf("Expected Result is:\n");    printf("Actual Result is: \n");    Print(NULL);    printf("\n");}//        100//        ///       50   //         \//         150void Test6(){    BinaryTreeNode* pNode100 = CreateBinaryTreeNode(100);    BinaryTreeNode* pNode50 = CreateBinaryTreeNode(50);    BinaryTreeNode* pNode150 = CreateBinaryTreeNode(150);    ConnectTreeNodes(pNode100, pNode50, NULL);    ConnectTreeNodes(pNode50, NULL, pNode150);    printf("====Test6 Begins: ====\n");    printf("Expected Result is:\n");    printf("100 \n");    printf("50 \n");    printf("150 \n\n");    printf("Actual Result is: \n");    Print(pNode100);    printf("\n");}int main(int argc, char* argv[]){    Test1();    Test2();    Test3();    Test4();    Test5();    Test6();return 0;}

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