lc 513 Find Bottom Left Tree Value

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

Example 1:

Input:

Output:

Example 2:

Input:

Output:

Note: You may assume the tree (i.e., the given root node) is not NULL.

BFS Accepted##

这个问题如果按照惯性思维从左到右进行BFS会陷入僵局，但是如果从右往左做BFS就特别简单，最下层的最左值即为最后一次从队列中出来的节点的值。

/**

 * 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*> q;

        q.push(root);

        auto temp = root;

        while (!q.empty()) {

            temp = q.front();

            q.pop();

            if (temp->right) q.push(temp->right);

            if (temp->left) q.push(temp->left);

        }

        return temp->val;

    }

};

巴特西

LN : leetcode 513 Find Bottom Left Tree Value

lc 513 Find Bottom Left Tree Value

BFS Accepted##

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