rt,实在想不出来,只有65分

#include <bits/stdc++.h>
#define int long long
using namespace std;
const int N = 1e6 + 10, mod = 1e9 + 7;
int mp[105][105], dp[105][105][2];
int dx[] = {1, -1, 0, 0}, dy[] = {0, 0, 1, -1};
int n, m;
bool vis[105][105][2];
int dfs(int x, int y, int now, bool ok)
{
    if (x == n && y == n)
        return 0;
    if (vis[x][y][now])
        return dp[x][y][now];
    vis[x][y][now] = true;
    for (int i = 0; i < 4; i++)
    {
        int xx = x + dx[i], yy = y + dy[i];
        if (xx < 1 || xx > n || yy < 1 || yy > n)
            continue;
        if (mp[xx][yy] == -1)
        {
            if (ok)
                continue;
            dp[x][y][now] = min(dp[x][y][now], dfs(xx, yy, now, true) + 2);
        }
        else if (mp[xx][yy] != -1 && mp[xx][yy] != now)
            dp[x][y][now] = min(dp[x][y][now], dfs(xx, yy, mp[xx][yy], false) + 1);
        else
            dp[x][y][now] = min(dp[x][y][now], dfs(xx, yy, now, false));
    }
    if (dp[x][y][now] >= 1e18)
        vis[x][y][now] = false;
    return dp[x][y][now];
}
signed main()
{
    std::ios::sync_with_stdio(false), cin.tie(0), cout.tie(0);
    cin >> n >> m;
    memset(mp, -1, sizeof mp);
    for (int i = 1; i <= n; i++)
        for (int j = 1; j <= n; j++)
            dp[i][j][0] = dp[i][j][1] = 1e18;
    for (int i = 1; i <= m; i++)
    {
        int a, b, c;
        cin >> a >> b >> c;
        mp[a][b] = c;
    }
    int res = dfs(1, 1, mp[1][1], false);
    if (res >= 1e18)
        cout << -1 << '\n';
    else
        cout << res << '\n';
    return 0;
}