LeetCode | 515. Find Largest Value in Each Tree Row 广度优先遍历

Youneed to find the largest value in each row of a binary tree.

Example:

Input:

 

          1

         / \

        3   2

       / \   \ 

      5   3   9

 

Output: [1, 3, 9]

这一题很简单，广度优先遍历就能解决，但是想要时间最短可不容易，这里假如使用queue来实现广度优先遍历的话，时间会变长，当时假如使用list链表来实现广度优先遍历的话，时间会缩短很多，以后在做只涉及到头尾的操作的时候，使用List 链表会很快，比如以后在广度优先遍历的时候使用List 链表会很快

class Solution {

public:

   vector<int> largestValues(TreeNode*root) {

      vector<int> result;

      if (root == NULL)  return result;

 

      queue< TreeNode *> store;

     

      TreeNode* p;

      store.push(root);

      int t = 1;

      int u = 0;

      int max=INT_MIN;

 

      while (!store.empty())

      {

            p = store.front();

            store.pop();

            t--;

            if (p->val > max) max =p->val;

 

            if (p->left != NULL) { store.push(p->left);u++; }

            if (p->right != NULL) {store.push(p->right); u++; }

 

            if (t == 0)

            {

                  result.push_back(max);

                  t = u;

                  max = INT_MIN;

                  u = 0;

            }

 

      }

      return result;

}

};