leetcode 111 Minimum Depth of Binary 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.

题解：注意没有的分支不算。

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    int dfs(TreeNode *r){
        if(r==NULL) return 0;
        if(r->left==NULL&&r->right==NULL){
            return 1;
        }
        else{
            if(r->left==NULL){
                return dfs(r->right)+1;
            }
            else if(r->right==NULL){
                return dfs(r->left)+1;
            }
            else{
                return min(dfs(r->left),dfs(r->right)) + 1;
            }
        }
    }

    int minDepth(TreeNode* root) {
        return dfs(root);
    }
};