111. Minimum Depth of Binary Tree

Problem

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.

Note: A leaf is a node with no children.

Example

Given binary tree [3,9,20,null,null,15,7],

    3
   / \
  9  20
    /  \
   15   7

return its minimum depth = 2.

Code

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
static int var = [](){
    std::ios::sync_with_stdio(false);
    cin.tie(NULL);
    return 0;
}();
class Solution {
public:
    int minDepth(TreeNode* root) {
        if(!root)
            return 0;

        return getMinDepth(root);
        
    }
    int getMinDepth(TreeNode* root){
        if(!root->left && !root->right)
            return 1;
        if(!root->left && root->right)
            return getMinDepth(root->right)+1;
        if(!root->right && root->left)
            return getMinDepth(root->left)+1;
        return min(getMinDepth(root->left),getMinDepth(root->right))+1;
    }
};

Result

111. Minimum Depth of Binary Tree.png