两个单链表，存在交点，求交点

/**
 *两个单链表有交点，用尽量高的效率查找到第一个交点
 */

#include <cmath>

struct node
{
	node* next;
};

int get_length(node* head)
{
	int sum=0;
	while(head)
	{
		++sum;
		head=head->next;
	}
	return sum;
}

node* find_common_node(node* left,node* right)
{
	if(left==nullptr || right=nullptr)
		return nullptr;
	int sum_left=get_length(left);
	int sum_right=get_length(right);
	/*int sub=abs(sum_left-sum_right);
	int sig=sum_left>sum_right?1:2;
	des_node=sig==1?left:right;
	while(sub)
	{
		des_node=dec_node->next;
	}*/
	while(sum_left>sum_right)
	{
		left=left->next;
		--sum_left;
	}
	while(sum_right>sum_left)
	{
		right=right->next;
		--sum_right;
	}
	while(left!=right)
	{
		left=left->next;
		right=right->next;
	}
	return left;
}