分行从上到下打印二叉树－C++

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// 面试题32（二）：分行从上到下打印二叉树 // 题目：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，每一层 // 打印到一行。 #include <cstdio> #include <queue> struct BinaryTreeNode { int m_nValue; BinaryTreeNode *m_pLeft; BinaryTreeNode *m_pRight; }; BinaryTreeNode *CreateBinaryTreeNode(int value) { BinaryTreeNode *pNode = new BinaryTreeNode(); pNode->m_nValue = value; pNode->m_pLeft = nullptr; pNode->m_pRight = nullptr; return pNode; } void ConnectTreeNodes(BinaryTreeNode *pParent, BinaryTreeNode *pLeft, BinaryTreeNode *pRight) { if (pParent != nullptr) { pParent->m_pLeft = pLeft; pParent->m_pRight = pRight; } } void PrintTreeNode(const BinaryTreeNode *pNode) { if (pNode != nullptr) { printf("value of this node is: %d\n", pNode->m_nValue); if (pNode->m_pLeft != nullptr) printf("value of its left child is: %d.\n", pNode->m_pLeft->m_nValue); else printf("left child is nullptr.\n"); if (pNode->m_pRight != nullptr) printf("value of its right child is: %d.\n", pNode->m_pRight->m_nValue); else printf("right child is nullptr.\n"); } else { printf("this node is nullptr.\n"); } printf("\n"); } void PrintTree(const BinaryTreeNode *pRoot) { PrintTreeNode(pRoot); if (pRoot != nullptr) { if (pRoot->m_pLeft != nullptr) PrintTree(pRoot->m_pLeft); if (pRoot->m_pRight != nullptr) PrintTree(pRoot->m_pRight); } } void DestroyTree(BinaryTreeNode *pRoot) { if (pRoot != nullptr) { BinaryTreeNode *pLeft = pRoot->m_pLeft; BinaryTreeNode *pRight = pRoot->m_pRight; delete pRoot; pRoot = nullptr; DestroyTree(pLeft); DestroyTree(pRight); } } void Print(BinaryTreeNode *pRoot) { if (pRoot == nullptr) 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 != nullptr) { nodes.push(pNode->m_pLeft); ++nextLevel; } if (pNode->m_pRight != nullptr) { nodes.push(pNode->m_pRight); ++nextLevel; } nodes.pop(); --toBePrinted; if (toBePrinted == 0) { printf("\n"); toBePrinted = nextLevel; nextLevel = 0; } } } // ====================测试代码==================== // 8 // 6 10 // 5 7 9 11 void 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 // 2 void Test2() { BinaryTreeNode *pNode5 = CreateBinaryTreeNode(5); BinaryTreeNode *pNode4 = CreateBinaryTreeNode(4); BinaryTreeNode *pNode3 = CreateBinaryTreeNode(3); BinaryTreeNode *pNode2 = CreateBinaryTreeNode(2); ConnectTreeNodes(pNode5, pNode4, nullptr); ConnectTreeNodes(pNode4, pNode3, nullptr); ConnectTreeNodes(pNode3, pNode2, nullptr); 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 // 2 void Test3() { BinaryTreeNode *pNode5 = CreateBinaryTreeNode(5); BinaryTreeNode *pNode4 = CreateBinaryTreeNode(4); BinaryTreeNode *pNode3 = CreateBinaryTreeNode(3); BinaryTreeNode *pNode2 = CreateBinaryTreeNode(2); ConnectTreeNodes(pNode5, nullptr, pNode4); ConnectTreeNodes(pNode4, nullptr, pNode3); ConnectTreeNodes(pNode3, nullptr, 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(nullptr); printf("\n"); } // 100 // / // 50 // \ // 150 void Test6() { BinaryTreeNode *pNode100 = CreateBinaryTreeNode(100); BinaryTreeNode *pNode50 = CreateBinaryTreeNode(50); BinaryTreeNode *pNode150 = CreateBinaryTreeNode(150); ConnectTreeNodes(pNode100, pNode50, nullptr); ConnectTreeNodes(pNode50, nullptr, 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; } // ------ Output ------ /* ====Test1 Begins: ==== Expected Result is: 8 6 10 5 7 9 11 Actual Result is: 8 6 10 5 7 9 11 ====Test2 Begins: ==== Expected Result is: 5 4 3 2 Actual Result is: 5 4 3 2 ====Test3 Begins: ==== Expected Result is: 5 4 3 2 Actual Result is: 5 4 3 2 ====Test4 Begins: ==== Expected Result is: 5 Actual Result is: 5 ====Test5 Begins: ==== Expected Result is: Actual Result is: ====Test6 Begins: ==== Expected Result is: 100 50 150 Actual Result is: 100 50 150 */