104. Maximum Depth of Binary Tree

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.

思路：這題本來要用ＤＦＳ解的，寫著寫著不知道為啥用了backtracking.......

class Solution {
public:
int _maxDepth;
int maxDepth(TreeNode* root) {

if(root == NULL) {
return 0;
}

int curDepth = 0;
solve(root, curDepth);
return _maxDepth;
}

void solve(TreeNode* tree, int& currentDepth) {
if(tree == NULL) {

_maxDepth = std::max(_maxDepth, currentDepth);
return;
}

currentDepth += 1;
solve(tree->left, currentDepth);
solve(tree->right, currentDepth);
currentDepth -= 1;
}

};