Tree Data Structure related must solve programming questions: Part - 1

LeetCode Problem #687

Given a binary tree find the longest possible path with same node values. The length of the path is determined the number of edges between the node.

Example 1:

Input:

              5
             / \
            4   5
           / \   \
          1   1   5

Output: 2

 

Example 2:

Input:

              1
             / \
            4   5
           / \   \
          4   4   5

Output: 2

Solution in C++:

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
 *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
 * };
 */
class Solution {
public:
    int longestUnivaluePath(TreeNode* root) {
        int maxi = 0;
        longestCalUtil(root, maxi);
        return maxi;
    }
    
    int longestCalUtil (TreeNode* node, int &maxi){
        if(!node)
            return 0;
        int l = longestCalUtil(node->left, maxi);
        int r = longestCalUtil(node->right, maxi);
            int left_max  = 0;
            int right_max = 0;
        if(node->left && node->left->val == node->val){
            left_max = l + 1;
        }
        if(node->right && node->right->val == node->val){
            right_max = r + 1;
        }
        maxi = max(maxi, left_max + right_max);
        return max(left_max, right_max);
    }
};

LeetCode Problem #111

Given a binary tree find the minimum depth of the tree. The depth of root node is zero.

Solution in C++:

/**

 * 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 minDepth(TreeNode* root) {

        if(!root)

            return 0;

        return Depth(root);

    }

    int Depth (TreeNode* root){

        if(!root)

            return INT_MAX - 1;

        if(!root->left && !root->right)

            return 1;

        return min(Depth(root->left), Depth(root->right)) + 1;

    }

};