文章作者:Tyan
博客:noahsnail.com | CSDN | 简书
1. Description
2. Solution
- Iterative
/**
* Definition for a binary tree node.
* struct TreeNode {
* int val;
* TreeNode *left;
* TreeNode *right;
* TreeNode(int x) : val(x), left(NULL), right(NULL) {}
* };
*/
class Solution {
public:
int findBottomLeftValue(TreeNode* root) {
queue<TreeNode*> currentLayer;
currentLayer.push(root);
while(!currentLayer.empty()) {
queue<TreeNode*> nextLayer;
int val = currentLayer.front()->val;
while(!currentLayer.empty()) {
TreeNode* node = currentLayer.front();
currentLayer.pop();
if(node->left) {
nextLayer.push(node->left);
}
if(node->right) {
nextLayer.push(node->right);
}
}
if(nextLayer.empty()) {
return val;
}
currentLayer = nextLayer;
}
}
};
- Recursive
/**
* Definition for a binary tree node.
* struct TreeNode {
* int val;
* TreeNode *left;
* TreeNode *right;
* TreeNode(int x) : val(x), left(NULL), right(NULL) {}
* };
*/
class Solution {
public:
int findBottomLeftValue(TreeNode* root) {
queue<TreeNode*> list;
list.push(root);
return findValue(list);
}
int findValue(queue<TreeNode*> currentLayer) {
int val = currentLayer.front()->val;
queue<TreeNode*> nextLayer;
while(!currentLayer.empty()) {
TreeNode* node = currentLayer.front();
currentLayer.pop();
if(node->left) {
nextLayer.push(node->left);
}
if(node->right) {
nextLayer.push(node->right);
}
}
if(nextLayer.empty()) {
return val;
}
else {
return findValue(nextLayer);
}
}
};