111. Minimum Depth of Binary Tree (Tree; DFS)

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.

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) return 0;
  
        min_depth = INT_MAX;
        dfs(root,1);
        return min_depth;
        
    }
    void dfs(TreeNode* node, int depth){
        if(node->left)
        {
            dfs(node->left,depth+1);
        }
       
        if(node->right)
        {           
            dfs(node->right,depth+1);
        }
        
        if(!node->left && !node->right)
        {
            if(depth < min_depth)
            {
                min_depth = depth;
            }        
        }
    }
private:
    int min_depth;
};