P4667 [BalticOI 2011 Day1]Switch the Lamp On

https://www.luogu.com.cn/record/93519277

Luogu/P4667/P4667.cpp

@@ -0,0 +1,76 @@
+#include <iostream>
+#include <algorithm>
+#include <queue>
+#include <vector>
+
+using std::cin;
+using std::cout;
+const char endl = '\n';
+
+const int N = 505;
+const int INF = 0x3f3f3f3f;
+
+int n, m, dist[N * N];
+std::vector<std::pair<int, int>> g[N * N];
+bool vis[N * N];
+
+int id(int x, int y) {
+    return x * (m + 1) + y;
+}
+
+void dijkstra() {
+    std::fill_n(dist, N * N, INF);
+
+    std::priority_queue<std::pair<int, int>, std::vector<std::pair<int, int>>, std::greater<std::pair<int, int>>> q;
+
+    q.emplace(0, id(0, 0));
+    dist[id(0, 0)] = 0;
+
+    while (!q.empty()) {
+        int u = q.top().second;
+        q.pop();
+
+        if (vis[u]) continue;
+        vis[u] = true;
+
+        for (auto e : g[u]) {
+            int v = e.first,
+                w = e.second;
+
+            if (dist[v] > dist[u] + w) {
+                dist[v] = dist[u] + w;
+                q.emplace(dist[v], v);
+            }
+        }
+    }
+}
+
+int main() {
+    std::ios::sync_with_stdio(false);
+    cin.tie(nullptr);
+
+    cin >> n >> m;
+
+    for (int i = 1; i <= n; i++) {
+        for (int j = 1; j <= m; j++) {
+            char c;
+
+            cin >> c;
+
+            g[id(i, j)].emplace_back(id(i - 1, j - 1), c != '\\');
+            g[id(i - 1, j - 1)].emplace_back(id(i, j), c != '\\');
+            g[id(i, j - 1)].emplace_back(id(i - 1, j), c != '/');
+            g[id(i - 1, j)].emplace_back(id(i, j - 1), c != '/');
+        }
+    }
+
+    dijkstra();
+
+    if (dist[id(n, m)] == INF) {
+        cout << "NO SOLUTION" << endl;
+    } else {
+        cout << dist[id(n, m)] << endl;
+    }
+
+    return 0;
+}