LeetCode-Sum of Left Leaves

最新推荐文章于 2023-02-25 22:41:55 发布

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本文介绍了一种使用队列遍历二叉树的方法来计算所有左叶子节点的值之和。通过逐层处理二叉树，可以有效地找出所有的左叶子节点并计算其总和。

题目大意：求二叉搜索树的左叶子节点的和

Find the sum of all left leaves in a given binary tree.

Example:

    3
   / \
  9  20
    /  \
   15   7

There are two left leaves in the binary tree, with values 9 and 15 respectively. Return 24.

一层一层采用队列的方式处理：

/**
 * 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 sumOfLeftLeaves(TreeNode* root) {
        int res = 0;
    if( root == NULL || root->left == NULL && root->right == NULL )
        return 0;
    queue<TreeNode*> q;
    q.push(root);
    while( !q.empty() ){
        TreeNode* node = q.front();
        q.pop();
        if( node->left != NULL && node->left->left == NULL  && node->left->right == NULL )
            res += node->left->val; 
        //将左右孩子入队
        if( node->left != NULL )
            q.push( node->left );
        if( node->right != NULL )
            q.push( node->right );
    }
    return res;
    }
};