LeetCode 513. Find Bottom Left Tree Value

Given a binary tree, find the leftmost value in the last row of the tree.
Example 1:
Input:
2
/ \
1 3
Output:
1
Example 2:
Input:
1
/ \
2 3
/ / \
4 5 6
/
7
Output:
7

题目大意：给一个二叉树，找它的最后一行的最左边的结点的值～

分析：广度优先搜索，对每一层进行遍历，result每次保存每一层的第一个值，最后层序遍历完成之后的result即为最后一行的第一个结点的值～

class Solution {
public:
    int findBottomLeftValue(TreeNode* root) {
        int result = root->val;
        queue<TreeNode *> q;
        q.push(root);
        TreeNode* temp;
        while (!q.empty()) {
            int size = q.size();
            result = q.front()->val;
            while (size--) {
                temp = q.front();
                q.pop();
                if (temp->left != NULL) q.push(temp->left);
                if (temp->right != NULL) q.push(temp->right);
            }
        }
        return result;
    }
};

class Solution {

public:

int findBottomLeftValue(TreeNode* root) {

int result = root->val;

queue<TreeNode *> q;

q.push(root);

TreeNode* temp;

while (!q.empty()) {

int size = q.size();

result = q.front()->val;

while (size--) {

temp = q.front();

q.pop();

if (temp->left != NULL) q.push(temp->left);

if (temp->right != NULL) q.push(temp->right);

}

return result;

}

};