【二叉树的递归】01二叉树的最小深度【Minimum Depth of Binary Tree】
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给定一个二叉树,找出他的最小的深度。
最小的深度,指的是从根节点到叶子节点的,经历的最小的节点个数。
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Given a binary tree, find its minimum depth.
The minimum depth is the number of nodes along the shortest path from the root node down to the nearest leaf node.
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test.cpp:
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#include <iostream>
#include <cstdio> #include <stack> #include <vector> #include <queue> #include "BinaryTree.h" using namespace std; int minDepth(TreeNode *root) { if(root == NULL) { return 0; } queue<TreeNode *> que; que.push(root); int count = 1; int depth = 0; while(!que.empty()) { TreeNode *tmp = que.front(); que.pop(); count--; if(tmp->left == NULL && tmp->right == NULL) { break; } if(tmp->left != NULL) { que.push(tmp->left); } if(tmp->right != NULL) { que.push(tmp->right); } /*count等于0说明这一层遍历完了,可以depth做加一操作*/ if(count == 0) { depth++; count = que.size(); } } depth++; return depth; } // 树中结点含有分叉, // 8 // / \ // 6 1 // / \ // 9 2 // / \ // 4 7 int main() { TreeNode *pNodeA1 = CreateBinaryTreeNode(8); TreeNode *pNodeA2 = CreateBinaryTreeNode(6); TreeNode *pNodeA3 = CreateBinaryTreeNode(1); TreeNode *pNodeA4 = CreateBinaryTreeNode(9); TreeNode *pNodeA5 = CreateBinaryTreeNode(2); TreeNode *pNodeA6 = CreateBinaryTreeNode(4); TreeNode *pNodeA7 = CreateBinaryTreeNode(7); ConnectTreeNodes(pNodeA1, pNodeA2, pNodeA3); ConnectTreeNodes(pNodeA2, pNodeA4, pNodeA5); ConnectTreeNodes(pNodeA5, pNodeA6, pNodeA7); cout << minDepth(pNodeA1) << endl; DestroyTree(pNodeA1); return 0; } |
结果输出:
2
BinaryTree.h:
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#ifndef _BINARY_TREE_H_
#define _BINARY_TREE_H_ struct TreeNode { int val; TreeNode *left; TreeNode *right; TreeNode(int x) : val(x), left(NULL), right(NULL) {} }; TreeNode *CreateBinaryTreeNode(int value); void ConnectTreeNodes(TreeNode *pParent, TreeNode *pLeft, TreeNode *pRight); void PrintTreeNode(TreeNode *pNode); void PrintTree(TreeNode *pRoot); void DestroyTree(TreeNode *pRoot); #endif /*_BINARY_TREE_H_*/ |
BinaryTree.cpp:
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#include <iostream>
#include <cstdio> #include "BinaryTree.h" using namespace std; /** * Definition for binary tree * struct TreeNode { * int val; * TreeNode *left; * TreeNode *right; * TreeNode(int x) : val(x), left(NULL), right(NULL) {} * }; */ //创建结点 TreeNode *CreateBinaryTreeNode(int value) { TreeNode *pNode = new TreeNode(value); return pNode; } //连接结点 void ConnectTreeNodes(TreeNode *pParent, TreeNode *pLeft, TreeNode *pRight) { if(pParent != NULL) { pParent->left = pLeft; pParent->right = pRight; } } //打印节点内容以及左右子结点内容 void PrintTreeNode(TreeNode *pNode) { if(pNode != NULL) { printf("value of this node is: %d\n", pNode->val); if(pNode->left != NULL) printf("value of its left child is: %d.\n", pNode->left->val); else printf("left child is null.\n"); if(pNode->right != NULL) printf("value of its right child is: %d.\n", pNode->right->val); else printf("right child is null.\n"); } else { printf("this node is null.\n"); } printf("\n"); } //前序遍历递归方法打印结点内容 void PrintTree(TreeNode *pRoot) { PrintTreeNode(pRoot); if(pRoot != NULL) { if(pRoot->left != NULL) PrintTree(pRoot->left); if(pRoot->right != NULL) PrintTree(pRoot->right); } } void DestroyTree(TreeNode *pRoot) { if(pRoot != NULL) { TreeNode *pLeft = pRoot->left; TreeNode *pRight = pRoot->right; delete pRoot; pRoot = NULL; DestroyTree(pLeft); DestroyTree(pRight); } } |