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 {
public:
    int minDepth(TreeNode *root) 
    {
        if(root==NULL) return 0;
        if(root->right==NULL && root->left==NULL) return 1;
        if(root->right==NULL) return 1+minDepth(root->left);
        if(root->left==NULL) return 1+minDepth(root->right);
        
        int dep1=1+minDepth(root->left);
        int dep2=1+minDepth(root->right);
        return dep1<dep2?dep1:dep2;
    }
    
};