题干

C++实现

#define _CRT_SECURE_NO_WARNINGS
#include<iostream>
#include<vector>
using namespace std;

struct TreeNode
{
	int num;
	TreeNode* left;
	TreeNode* right;
	TreeNode* parent;
};

void createTree(vector<TreeNode*>& nodeArr, int n) {
	for (int j = 1; j <= n; j++)
	{
		nodeArr[j] = new TreeNode;
		nodeArr[j]->num = j;
	}

	nodeArr[1]->parent = NULL;
	for (int j = 1; j <= n; j++)
	{
		int left, right;
		cin >> left >> right;
		if (left != -1) {
			nodeArr[j]->left = nodeArr[left];
			nodeArr[left]->parent = nodeArr[j];
		}
		else {
			nodeArr[j]->left = NULL;
		}
		if (right != -1) {
			nodeArr[j]->right = nodeArr[right];
			nodeArr[right]->parent = nodeArr[j];
		}
		else {
			nodeArr[j]->right = NULL;
		}
	}
}

int main() {
	int t;//t组测试数据
	cin >> t;
	for (int i = 0; i < t; i++)
	{
		int n, m;//n是用来建树，m是用来找最短路径
		cin >> n >> m;
		vector<TreeNode*> nodeArr(n + 1);
		createTree(nodeArr, n);
		
		int lhs, rhs;
		for (int j = 0; j < m; j++)
		{
			cin >> lhs >> rhs;
			vector<int> lvec;
			TreeNode* p = nodeArr[lhs];
			while (p != NULL) {
				lvec.push_back(p->num);
				p = p->parent;
			}

			vector<int> rvec;
			p = nodeArr[rhs];
			while (p != NULL) {
				rvec.push_back(p->num);
				p = p->parent;
			}

			int l = lvec.size() - 1;
			int r = rvec.size() - 1;
			while (1) {
				if (l < 0 || r < 0 || lvec[l] != rvec[r]) {
					break;
				}
				--l;
				--r; 
			}
			cout << l + r + 2;
		}
	}

	return 0;
}