题目描述
输入一棵二叉树，求该树的深度。从根结点到叶结点依次经过的结点（含根、叶结点）形成树的一条路径，最长路径的长度为树的深度。
解题思路
- 递归求树的深度
/*
struct TreeNode {
int val;
struct TreeNode *left;
struct TreeNode *right;
TreeNode(int x) :
val(x), left(NULL), right(NULL) {
}
};*/
class Solution {
public:
int TreeDepth(TreeNode* pRoot)
{
if(pRoot == NULL){
return 0;
}
int leftDepth = TreeDepth(pRoot -> left);
int rightDepth = TreeDepth(pRoot -> right);
return leftDepth > rightDepth ? leftDepth + 1 : rightDepth + 1;
}
};
非递归求深度
- 借助辅助栈
- 按照层次遍历 每次弹出该层的所有元素 然后level++
- 最后输出level即可
/*
struct TreeNode {
int val;
struct TreeNode *left;
struct TreeNode *right;
TreeNode(int x) :
val(x), left(NULL), right(NULL) {
}
};*/
class Solution {
public:
int TreeDepth(TreeNode* pRoot)
{
if(pRoot == NULL){
return 0;
}
queue<TreeNode*> q;
q.push(pRoot);
int level = 0;
while(!q.empty()){
int size = q.size();
for(int i = 0; i < size; i++){
TreeNode* t = q.front();
q.pop();
if(t -> left){
q.push(t -> left);
}
if(t -> right){
q.push(t -> right);
}
}
level++;
}
return level;
}
};
