[LeetCode] Minimum Depth of Binary Tree

Given a binary tree, find its minimum depth.

The minimum depth is the number of nodes along the shortest path from the root node down to the nearest leaf node.

Solution:

/**

 * Definition for binary tree

 * struct TreeNode {

 *     int val;

 *     TreeNode *left;

 *     TreeNode *right;

 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}

 * };

 */

class Solution {

public:

    int min = 2147483647;

    void calc(int depth, TreeNode *node)

    {

        if(node == NULL) return;

        if(node -> left == NULL && node -> right == NULL)

        {

            if(depth < min)

                min = depth + 1;

        }

        else

        {

            if(node -> left != NULL)

                calc(depth + 1, node -> left);

            if(node -> right != NULL)

                calc(depth + 1, node -> right);

        }

    }

    

    int minDepth(TreeNode *root) {

        if(root == NULL) return 0;

        calc(0, root);

        return min;

    }

};