Find Bottom Left Tree Value

Find Bottom Left Tree Value

A.题意

Given a binary tree, find the leftmost value in the last row of the tree.

Example 1:

Input:

2

/ \

1 3

Output:

1

Example 2:

Input:

1
/ \
2   3
/   / \
4   5   6
/
7

Output:

7

B.思路

树搜索问题，这里我们用队列模拟搜索，进行宽度优先搜索，然后让左节点先进队列并且每次保证赋值给返回值的值都是先赋值左边那个的。

C.代码实现

/**
* 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) {
if (!root) return 0;
int res = 0;
queue<TreeNode*> q;
q.push(root);
while (!q.empty())
{
int n = q.size();
for (int i = 0;i < n;i++)
{
TreeNode* t = q.front();
q.pop();
if (i == 0) res = t->val;
if (t->left) q.push(t->left);
if (t->right) q.push(t->right);
}
}
return res;
}
};