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Maximum Depth of Binary Tree

2014-02-27 16:46 211 查看
Given a binary tree, find its maximum depth.

The maximum depth is the number of nodes along the longest path from the root node down to the farthest leaf node.

递归方法,分别求左子树和右子树的深度,然后取二者中大的一个,然后加1就是二叉树的深度。

/**
* Definition for binary tree
* struct TreeNode {
*     int val;
*     TreeNode *left;
*     TreeNode *right;
*     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
* };
*/
class Solution {
public:
int maxDepth(TreeNode *root) {
int depth = 0;
if(root)
{
int lDepth = maxDepth(root -> left);
int rDepth = maxDepth(root -> right);
if(lDepth >= rDepth)
depth = lDepth+1;
else
depth = rDepth+1;
}

return depth;

}
};

非递归,利用树的层序遍历,来求最大深度

/**
* Definition for binary tree
* struct TreeNode {
*     int val;
*     TreeNode *left;
*     TreeNode *right;
*     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
* };
*/

struct Node
{
TreeNode *node;
int level;
Node(){}
Node(TreeNode *n, int l):node(n), level(l){}
};

class Solution {

public:
int maxDepth(TreeNode *root){
// Start typing your C/C++ solution below
// DO NOT write int main() function

if (root == NULL)
return 0;

queue<Node> q;

q.push(Node(root, 1));

int curLevel = 0;

while(!q.empty())
{
Node node = q.front();
if (node.node->left)
q.push(Node(node.node->left, node.level + 1));
if (node.node->right)
q.push(Node(node.node->right, node.level + 1));

if (curLevel != node.level)
{

curLevel = node.level;

}

q.pop();
}

return curLevel;
}
};
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