代码随想录：二叉树的最小深度

/**
 * 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 minDepth(TreeNode* root) {
        queue<TreeNode*> que;
        if (root)
            que.push(root);
        else {
            return 0;
        }

        int height = 0;
        int res = 100000;
        while (!que.empty()) {
            int size = que.size();
            height++;
            while (size > 0) {
                TreeNode* target = que.front();
                if (target->left)
                    que.push(target->left);
                if (target->right)
                    que.push(target->right);
                if (target->left == NULL && target->right == NULL) {
                    res = min(res, height);
                }
                que.pop();
                size--;
            }
        }
        return res;
    }
};