findBottomLeftValue.cpp

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
 *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
 * };
 */
class Solution {
public:
    int findBottomLeftValue(TreeNode* root) {
        queue<TreeNode*> q;
        q.push(root);
        int left;
        while (!q.empty()) {
            int len = q.size();
            left = q.front() -> val;
            for (int i = 0; i < len; i++) {
                TreeNode *node = q.front();
                q.pop();
                if (node -> left) q.push(node -> left);
                if (node -> right) q.push(node -> right);
            }
        }
        return left;
    }
};

// Recursion
class Solution {
public:
    int maxLen = INT_MIN;
    int maxleftValue;
    void traversal(TreeNode* root, int leftLen) {
        if (!root->left && !root->right) {
            if (leftLen > maxLen) {
                maxLen = leftLen;
                maxleftValue = root->val;
            }
            return;
        }
        if (root->left) {
            traversal(root->left, leftLen + 1); 
        }
        if (root->right) {
            traversal(root->right, leftLen + 1);
        }
        return;
    }
    int findBottomLeftValue(TreeNode* root) {
        traversal(root, 0);
        return maxleftValue;
    }
};

// 作者：carlsun-2
// 链接：https://leetcode-cn.com/problems/find-bottom-left-tree-value/solution/dai-ma-sui-xiang-lu-dai-ni-xue-tou-er-ch-w3og/
// 来源：力扣（LeetCode）
// 著作权归作者所有。商业转载请联系作者获得授权，非商业转载请注明出处。