Minimum Depth of Binary Tree.cpp

// Minimum Depth of Binary Tree


//be careful to check if the node is leaf, and NULL is not leaf.
int minDepth(TreeNode *root) {
    if(root == NULL){
        return 0;
    }
    if(root->left == NULL && root->right == NULL){
        return 1;
    }
    if(root->left == NULL){
        return 1 + minDepth(root->right);
    }
    if(root->right == NULL){
        return 1 + minDepth(root->left);
    }
    return 1 + min(minDepth(root->left), minDepth(root->right));
}