Code:

#include <iostream>
#include <cstring>
#include <algorithm>
#include <queue>

const int dx[4] = {-1, 0, 1, 0}, dy[4] = {0, 1, 0, -1};
const int N = 1010, TN = 2 * N;

typedef std::pair<int, int> PII;

int T, n;
bool g[N][N], vis[N][N];
PII zz[TN];

struct Node { int x, y, times; };

bool bfs()
{
    std::queue<Node> q;
    q.push((Node){1, 1, 0});
    vis[1][1] = 1;
    while (q.size())
    {
        auto t = q.front(); q.pop();
        if (t.x == n && t.y == n) return true;
		g[zz[t.times - 1].first][zz[t.times - 1].second] = 1;
        for (int i = 0; i < 4; i ++ )
        {
            int xx = t.x + dx[i], yy = t.y + dy[i];
            if (xx >= 1 && xx <= n && yy >= 1 && yy <= n && !g[xx][yy] && !vis[xx][yy])
            {
                vis[xx][yy] = true;
                q.push((Node){xx, yy, t.times + 1});
            }
        }
    }
    return false;
}

int main()
{
    scanf("%d", &T);
    while (T -- )
    {
        memset(vis, 0, sizeof vis);
        memset(g, -1, sizeof g);
        scanf("%d", &n);
        for (int i = 0; i < 2 * n - 2; i ++ )
            scanf("%d%d", &zz[i].first, &zz[i].second);
		if (bfs()) puts("Yes");
        else puts("No");
    }
    return 0;
}