graph, SCC

Author: tjd229

TopCoder/Autogame.cpp

@@ -0,0 +1,79 @@
+//category : graph, SCC
+
+#include <vector>
+#include <algorithm>
+#define ll long long
+using namespace std;
+const int mod = 1e9 + 7;
+class Autogame{
+public:
+	vector<int> edge;
+	vector<int> back[50];
+	int K;
+	int visit[50];
+	int from[50];
+	int back_dfs(int ix,int src,int sz,int depth,int *seat){
+		ll res = 1;
+		visit[ix] = 2;
+		seat[sz-1+depth] = 1;
+		for (int i = 0; i < back[ix].size(); i++){
+			//if (visit[back[ix][i]] == 2) continue;
+			res *= back_dfs(back[ix][i], src, sz, depth+1,seat);
+		}
+		if (depth > K) seat[sz-1 + depth - K]++;
+		else seat[(src+K-depth)%sz]++;
+		return res*seat[sz-1+depth]%mod;
+	}
+	int dfs(int ix){
+		if (visit[ix]) return 1;
+		visit[ix] = 1;
+		ll res = 1;
+		if (visit[edge[ix]] == 1){
+			int stk = ix;
+			vector<int> scc;
+			scc.push_back(ix);
+			visit[ix] = 2;
+			while (stk != edge[ix]){
+				stk = from[stk];
+				visit[stk] = 2;
+				scc.push_back(stk);
+			}
+			reverse(scc.begin(), scc.end());
+			int seat[50] = { 0 };
+			int i, j;
+			for (i = 0; i < scc.size(); i++){
+				for (j = 0; j < back[scc[i]].size(); j++){
+					int to = back[scc[i]][j];
+					if (visit[to] == 2) continue;
+					res = res*back_dfs(to,i,scc.size(),1,seat);
+				}
+				seat[i]+=2;
+			}
+			for (i = 0; i < scc.size(); i++) res = res*seat[i] % mod;
+			return res;
+		}
+		else{
+			from[edge[ix]] = ix;
+			return dfs(edge[ix]);
+		}		
+	}
+	int wayscnt(vector<int> a, int K){
+
+		int i;
+		for (i = 0; i < a.size(); i++){
+			visit[i] = 0;
+			a[i]--;
+			back[a[i]].push_back(i);
+		}
+		this->edge = a;
+		this->K = K;
+		ll res = 1;
+		for (i = 0; i < a.size(); i++){
+			//from[i] = -1;
+			res = res*dfs(i) % mod;
+		}
+		
+		return res;
+	}
+
+};