Likou 513. Find the value in the lower left corner of the tree

topic:

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

Example:

Input:
2
/\
1 3

Output:
1

solution

The topic requires [find the last line], [the value of the leftmost node]
think of the layer sequence traversal.
Each time the layer sequence is traversed, record the leftmost value.

Code

class Solution {
    
    
public:
    int findBottomLeftValue(TreeNode* root) {
    
    
        queue<TreeNode*> que;
        if(root) que.push(root);
        int result = 0;

        while(!que.empty()) {
    
    
            int size = que.size();
            for (int i = 0; i < size; i++) {
    
    
                TreeNode* node = que.front();
                que.pop();
                if (i == 0) result = node->val;

                if (node->left) que.push(node->left);
                if (node->right) que.push(node->right);               
            }
        }
        return result;
    }
};