leetcode_129_Sum Root to Leaf Numbers

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Sum Root to Leaf Numbers

Given a binary tree containing digits from 0-9 only, each root-to-leaf path could represent a number.

An example is the root-to-leaf path 1->2->3 which represents the number 123.

Find the total sum of all root-to-leaf numbers.

For example,

    1
   / \
  2   3
The root-to-leaf path 1->2 represents the number 12.
The root-to-leaf path 1->3 represents the number 13.

Return the sum = 12 + 13 = 25.

class Solution {
public:
    int sumNumbers(TreeNode *root) {
		if(root!=NULL)
			sumNumbersUtil( root , 0 );
		return ans;
    }
private:
	int ans=0;
	void sumNumbersUtil(TreeNode *root , int cur)
	{
		if(!root)
			return;
		if(root->left!=NULL || root->right!=NULL)
		{
			sumNumbersUtil(root->left,  cur*10 + root->val);
			sumNumbersUtil(root->right, cur*10 + root->val);
		}
		else
			ans += cur*10 + root->val;
	}
};

//另一种写法
class Solution {
public:
    int sumNumbers(TreeNode *root) {
		int ans=0;
		if(root!=NULL)
			sumNumbersUtil( root , 0 , ans);
		return ans;
    }
private:
	
	void sumNumbersUtil(TreeNode *root , int cur ,int& ans)
	{
		if(!root)
			return;
		if(root->left!=NULL || root->right!=NULL)
		{
			sumNumbersUtil(root->left,  cur*10 + root->val , ans);
			sumNumbersUtil(root->right, cur*10 + root->val , ans);
		}
		else
			ans += cur*10 + root->val;
	}
};