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| #include <bits/stdc++.h>
using namespace std;
const int LEN = 350;
int ans = -1, vis[LEN][LEN], table[LEN][LEN], walk[4][2] = {{-1, 0}, {0, -1}, {0, 1}, {1, 0}};
struct Node
{
int x_, y_, t_;
Node(int x, int y, int t) : x_(x), y_(y), t_(t) {}
};
queue<Node> q;
void init()
{
memset(table, -1, sizeof(table));
int n, x, y, t;
cin >> n;
while (n--)
{
cin >> x >> y >> t;
if (table[x][y] == -1)
table[x][y] = t;
else
table[x][y] = min(t, table[x][y]);
for (int i = 0; i < 4; ++i)
{
int nxt_x = x + walk[i][0], nxt_y = y + walk[i][1];
if (nxt_x < 0 || nxt_y < 0)
continue;
table[nxt_x][nxt_y] = table[nxt_x][nxt_y] == -1 ? t : min(table[nxt_x][nxt_y], t);
}
}
q.emplace(0, 0, 0);
vis[0][0] = 1;
}
void bfs()
{
while (!q.empty())
{
Node u = q.front();
q.pop();
int ux = u.x_, uy = u.y_, ut = u.t_;
if (table[ux][uy] == -1)
{
ans = ut;
return;
}
for (int i = 0; i < 4; ++i)
{
int x = ux + walk[i][0], y = uy + walk[i][1], t = ut + 1;
if (x < 0 || y < 0 || vis[x][y] || (table[x][y] != -1 && table[x][y] <= t))
continue;
q.emplace(x, y, t);
vis[x][y] = 1;
}
}
}
int main()
{
init();
bfs();
cout << ans << endl;
return 0;
}
|