漫画讲解C语言中最近公共祖先的三种类型

//三叉链
struct TreeNode {
    int val;
    TreeNode *left;
    TreeNode *right;
	TreeNode *parent;
    TreeNode(int x) : val(x), left(NULL), right(NULL), parent(NULL) {}
};
class Solution {
public:
	TreeNode* lowestCommonAncestor(TreeNode* root, TreeNode* p, TreeNode* q) {
		TreeNode* curp = p, *curq = q; //用于遍历p、q结点的祖先结点
		int lenp = 0, lenq = 0; //分别记录p、q结点各自的祖先结点个数
		//统计p结点的祖先结点个数
		while (curp != root)
		{
			lenp++;
			curp = curp->parent;
		}
		//统计q结点的祖先结点个数
		while (curq != root)
		{
			lenq++;
			curq = curq->parent;
		}
		//longpath和shortpath分别标记祖先路径较长和较短的结点
		TreeNode* longpath = p, *shortpath = q;
		if (lenp < lenq)
		{
			longpath = q;
			shortpath = p;
		}
		//p、q结点祖先结点个数的差值
		int count = abs(lenp - lenq);
		//先让longpath往上走count个结点
		while (count--)
		{
			longpath = longpath->parent;
		}
		//再让longpath和shortpath同时往上走，此时第一个相同的结点便是最近公共祖先结点
		while (longpath != shortpath)
		{
			longpath = longpath->parent;
			shortpath = shortpath->parent;
		}
		return longpath; //返回最近公共祖先结点
	}
};