HDU 1269 迷宫城堡（强连通）

HDU 1269 迷宫城堡

题目链接

题意：中文题

思路：强连通模板题

代码：

#include <cstdio>#include <cstring>#include <vector>#include <stack>using namespace std;const int N = 10005;int n, m;vector<int> g[N], scc[N];int pre[N], lowlink[N], sccno[N], dfs_clock, scc_cnt;stack<int> S;void dfs_scc(int u) {pre[u] = lowlink[u] = ++dfs_clock;S.push(u);for (int i = 0; i < g[u].size(); i++) {int v = g[u][i];if (!pre[v]) {dfs_scc(v);lowlink[u] = min(lowlink[u], lowlink[v]);} else if (!sccno[v])lowlink[u] = min(lowlink[u], pre[v]);}if (lowlink[u] == pre[u]) {scc_cnt++;int x = S.top();while (x != u) {sccno[x] = scc_cnt;S.pop();x = S.top();}}}void find_scc(int n) {dfs_clock = scc_cnt = 0;memset(sccno, 0, sizeof(sccno));memset(pre, 0, sizeof(pre));for (int i = 1; i <= n; i++)if (!pre[i]) dfs_scc(i);}int main() {while (~scanf("%d%d", &n, &m) && n || m) {int u, v;for (int i = 1; i <= n; i++) g[i].clear();while (m--) {scanf("%d%d", &u, &v);g[u].push_back(v);}find_scc(n);if (scc_cnt <= 1) printf("Yes\n");else printf("No\n");}return 0;}