111二叉树的最小深度.cpp

class Solution {
public:
    int minDepth(TreeNode* root) {
        if (root == NULL) return 0;
        if (root->left == NULL) return minDepth(root->right) + 1;
        if (root->right == NULL) return minDepth(root->left) + 1;
        return min(minDepth(root->left), minDepth(root->right)) + 1;
    }
};