30 Day Challenge Day 2 | Leetcode 1302. Deepest Leaves Sum

题解

非常典型的二叉树遍历的题，BFS做起来更顺手一些，DFS处理起来要稍稍注意些。

BFS

class Solution {
public:
    int deepestLeavesSum(TreeNode* root) {
        if(!root) return 0;

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

DFS

class Solution {
public:
    int deepestLeavesSum(TreeNode* root) {
        int level = 0, deepest = 0, sum = 0;
        deepestSum(root, level, deepest, sum);
        return sum;
    }
    
    void deepestSum(TreeNode* node, int level, int &deepest, int &sum) {
        if(!node) return;
        
        level += 1;
        
        if(level == deepest) {
            sum += node->val;
        } else if (level > deepest) {
            sum = node->val;
            deepest = level;
        }
        
        deepestSum(node->left, level, deepest, sum);
        deepestSum(node->right, level, deepest, sum);
    }
};