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.

/**
 * Definition for binary tree
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
private: int minD=INT_MAX;
public:
    void dfs(TreeNode* node,int curD){
        if(!node) return;
        if(!node->left&&!node->right&&curD+1<minD){
            minD=curD+1;
            return;
        }
        dfs(node->left,curD+1);
        dfs(node->right,curD+1);
    }
    int minDepth(TreeNode *root) {
        if(!root) return 0;
        dfs(root,0);
        return minD;
    }
};