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.

　　

/**

 * 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) {

        // Start typing your C/C++ solution below

        // DO NOT write int main() function

        if(root == NULL) return 0;

        int leftNum = 1 + minDepth(root->left) ;

        int rightNum = 1 + minDepth(root->right);

        

        //排除非叶子节点的情况

        if(root->left == NULL) return rightNum;

        if(root->right == NULL ) return leftNum ;

        

        int result = leftNum < rightNum ? leftNum: rightNum ;

        

        return result ;

    }

};

 重写后 ：主要是为了强化路径的定义而重写

class Solution {

public:

   void DFS(TreeNode * root, int len){

            

        if(root->left== NULL && root->right == NULL ){

            res = res < len ? res : len;

            return;

        }

        if(root->left != NULL)

            DFS(root->left, len +1);

        if(root->right != NULL)

            DFS(root->right, len+1);

    }

    int minDepth(TreeNode *root) {

        // Start typing your C/C++ solution below

        // DO NOT write int main() function

        if(root == NULL ) return 0;

        res = INT_MAX;

        DFS(root, 1);

        return res;

    }

private:

    int res;

};