✨ P3465

Author: CodingOIer

Problem/Luogu/P3465.cpp

@@ -0,0 +1,116 @@
+#include <cstdio>
+#include <tuple>
+#include <vector>
+constexpr int MaxN = 1e5 + 5;
+int n, m;
+int answer[MaxN];
+bool vis[MaxN];
+std::vector<int> g[MaxN];
+void dfsSet(int u, int f)
+{
+    if (vis[u])
+    {
+        return;
+    }
+    vis[u] = true;
+    answer[u] = f;
+    for (const auto &v : g[u])
+    {
+        if (v == f)
+        {
+            continue;
+        }
+        dfsSet(v, u);
+    }
+}
+std::tuple<bool, int, bool> dfs(int u, int f)
+{
+    if (vis[u])
+    {
+        answer[u] = f;
+        return {true, u, false};
+    }
+    vis[u] = true;
+    bool suc = false;
+    for (const auto &v : g[u])
+    {
+        if (v == f)
+        {
+            continue;
+        }
+        auto [found, c, pass] = dfs(v, u);
+        if (found)
+        {
+            if (c == u)
+            {
+                pass = true;
+            }
+            if (f == 0)
+            {
+                suc = true;
+                break;
+            }
+            if (pass)
+            {
+                answer[f] = u;
+            }
+            if (!pass)
+            {
+                answer[u] = f;
+            }
+            for (const auto &v : g[u])
+            {
+                if (v == f)
+                {
+                    continue;
+                }
+                dfsSet(v, u);
+            }
+            return {found, c, pass};
+        }
+    }
+    vis[u] = false;
+    if (f == 0 && suc)
+    {
+        vis[u] = true;
+        for (const auto &v : g[u])
+        {
+            if (v == f)
+            {
+                continue;
+            }
+            dfsSet(v, u);
+        }
+        return {true, 0, false};
+    }
+    return {false, 0, false};
+}
+int main()
+{
+    scanf("%d%d", &n, &m);
+    for (int i = 1; i <= m; i++)
+    {
+        int u, v;
+        scanf("%d%d", &u, &v);
+        g[u].push_back(v);
+        g[v].push_back(u);
+    }
+    for (int i = 1; i <= n; i++)
+    {
+        if (!vis[i])
+        {
+            const auto &[res, _a, _b] = dfs(i, 0);
+            if (!res)
+            {
+                printf("NIE\n");
+                return 0;
+            }
+        }
+    }
+    printf("TAK\n");
+    for (int i = 1; i <= n; i++)
+    {
+        printf("%d\n", answer[i]);
+    }
+    return 0;
+}