add Topological Sort template

Author: Clouder0

templates/TopoSort.cpp

@@ -0,0 +1,38 @@
+#include <cstdio>
+
+const int maxn = 1e5 + 100;
+struct node
+{
+    int to, next;
+} E[maxn];
+int head[maxn], cnt;
+inline void add(const int& u, const int& v)
+{
+    E[++cnt].next = head[u], head[u] = cnt, E[cnt].to = v;
+}
+
+int n, m;
+
+namespace Topo
+{
+int in[maxn], q[maxn], qh, qt;
+void TopoSort()
+{
+    for (int i = 1; i <= n; ++i) in[i] = 0;
+    for (int u = 1; u <= n; ++u)
+        for (int p = head[u]; p; p = E[p].next) ++in[E[p].to];
+    qh = 1, qt = 0;
+    for (int i = 1; i <= n; ++i)
+        if (!in[i]) q[++qt] = i;
+    while (qh >= qt)
+    {
+        int u = q[qh++];
+        for (int p = head[u]; p; p = E[p].next)
+        {
+            int v = E[p].to;
+            if (--in[v] == 0)
+                q[++qt] = v;
+        }
+    }
+}
+}  // namespace Topo